GB2084502A - A chain pin extractor - Google Patents

Abstract

An extractor, for driving a pin out of link and side wall elements of a chain, has a body with opposed spaced portions 2, 3. One body portion 2 has a seating 9 with a bore opening 10 at a radical abutment face. A sleeve 6 is threaded through the other body portion 3 and has one end provided with a coaxial bore 16 opening at an abutment face. A stem 12 is threaded in the sleeve 6 and carries a push rod 17, which is a close-tolerance sliding fit in the bore of the sleeve. The seating may be provided as an insert collar, and the bore and abutment face of the sleeve may be provided on a locating bushing 15 carried by the sleeve. When a chain (18, fig 2) is gripped between the abutment faces, and with the usual protruding end of the pin (24) engaged in the bores of the seating and of the sleeve, the push rod is centered accurately with respect to the chain pin, and is guided and supported against buckling by its close-tolerance sliding fit in the sleeve. <IMAGE>

Description

SPECIFICATION A chain pin extractor This invention relates to an extractor for driving a link pin out of chain elements which are coupled by the pin.

The conventional construction of a roller chain has link elements in which two sleeves, each having a rolleriournalled thereon, are coupled by side wall members secured on the sleeves. Each link element is connected to the next link element by another pair of side wall members which are connected very securely together by a respective pin which is engaged solidly with those members but which is a clearance fit in the sleeve. The pin protrudes at each end from the side wall members with which it is engaged, and those end portions are deformed, after assembly, so as to act somewhat in the manner of a rivet head.

When it is desired to separate the link elements, or as it is known in the art "to break the chain", the pin must be extracted by pushing it axially out of the assembled elements. Due to the deformed ends, and the general tight fit of the pin within the side wall members, the force required to push the pin axially out of the chain can be extremely high.

The diameter of the pin may be quite small, say of the order of three millimetres in a three-eighths inch pitch chain, and the exposed end of the pin is often somewhat rounded due to deformation when securing. It is necessary (a) to use a pushing tool which is not greater in diameter than the chain pin, (b) to ensure that the pushing tool is guided axially and supported against any tendency to buckle under the high axial forces applied, and (c) to ensure that the pushing tool is initially precisely centered on the pin and is held thus during at least commencement of the extraction operation.

It is accordingly the object of the present invention to provide an improved construction of chain pin extractor which fulfills these requirements.

The applicant is aware of British Patent Specification No. 11 63249 which discloses a rivet extractor comprising a generally "C" shaped body having one end portion formed as an anvil, a tubular clamping screw extending through a threaded hole in the other end portion of the body able to be advanced axially towards said anvil, a pressure screw extending axially into said clamping screw from one end and a punch element adapted to be projected beyond the other end of said clamping screw by rotation of said pressure screw, said anvil having a rivet discharge passage extending through it with one end opening to the anvil's working surface in alignment with said punch element.The preferred embodiment has the punch element as a separate pin punch loosely trapped within the clamping screw, but in other embodiments it may be a pin integral with the pressure screw and extending coaxially therefrom. The pinch punch is not described as being otherwise than "loosely trapped" within the bore of the clamping screw, and in the illustrated embodiments the diameter of the bore of the clamping screw appears to be of the order of 4050% greater than the diameter of the pinch punch. In the example given of use of the device, two pieces of sheet metal are shown as riveted together by a rivet having a hemispherical head still remaining on one end, and it is stated that it is assumed that the other head of the rivet has already been removed in any conventional manner.The remaining head of the rivet is positioned in a passage of the anvil the diameter of which is of the order of 5060% greater than the diameter of the rivet head. The pressure screw is then advanced through the clamping screw to bring the pin punch into engagement with the rivet, whereupon the pressure screw may be further advanced to drive out the rivet. It is considered that it will be clear to a person skilled in the art of roller chain construction that such a rivet extractor cannot fulfill the requirements of ensuring that the pushing tool is guided axially and supported against any tendency to buckle, or of ensuring that the pushing tool is initially precisely centered on the item to be extracted and is held thus during at least commencement of the extraction operation.

According to the present invention a chain pin extractor comprises a body having first and second opposed spaced portions, a seating of the first body portion having a bore opening at a radial abutment face opposed to the second body portion, a sleeve movable axially in the second body portion towards and away from the first body portion and having one end portion nearer the first body portion provided with a coaxial bore opening at a radial abutment face opposed to the first body portion, and a stem movable axially in the sleeve and carrying a push rod which is a close-tolerance sliding fit in the bore of the sleeve.

With such an arrangement, the push rod is guided axially and is supported against any tendency to buckle laterally under the high axial forces which are usually required to push a pin out of a chain. Further, as the protruding end of the chain pin may be introduced into the bore of the sleeve, the push rod and chain pin are held in axial alignment. It will be appreciated that a sleeve having a bore closely related to the diameter of the chain pin may be adopted. In a preferred arrangement, the coaxial bore and radial abutment face of the sleeve are provided on a locating bushing forming an insert in the sleeve, either as a sliding fit or threaded removably therein, whereby the same sleeve can then be used with push rods of a range of different diameters and provide a close-tolerance sliding fit with each of the push rods.

A plurality of stems may be provided, each being adapted to move within the sleeve but each being provided with a push rod of a different diameter, to match up with the bore of an associated locating bush.

Advantageously, the bore and radial abutment face of the seating are provided on a seating collar which is inserted in an opening of the first portion of the body. The collar may be removably inserted in the body portion, either as a sliding fit or by a screw-threaded engagement, whereby there may be provided, for use with a single body, a plurality of collars each having a bore of a different diameter corresponding to a locating bush and its associated push rod.

The sleeve is most conveniently moved relative to the body by threading it in the respective body portion, and rotating it in the appropriate direction to obtain axial movement as required. Similarly, the stem is most conveniently moved relative to the sleeve by threading it in the sleeve.

in order that the nature of the invention may be readily ascertained, an embodiment of chain pin extractor in accordance therewith is hereinafter particularly described with reference to the accompanying drawing, wherein: Fig. 1 is a side elevation with parts shown in section; Fig. 2 is a sectional view, to a much enlarged scale, of a locating bush, chain elements, and a seating collar The extractor comprises a body 1, which is conveniently made as a moulding of cast iron, having two spaced legs 2, 3 connected by a bridge 3 having a handle 4. The handle 4 is advantageously made with plane parallel faces so as to facilitate gripping in a vice if desired.

The leg 1 has a threaded bore 5 in which is received a threaded sleeve 6 carrying a lock nut 7.

The leg 2 has an opening 8 which is coaxial with the bore 5 and which has a seating collar 9 disposed therein. Preferably but not necessarily the seating collar 9 is secured in the opening 8, e.g. by adhesive. The seating collar 9 has a passage 10 which is coaxial with the bore 5 and opening 8.

The sleeve 6 has a threaded bore 11 in which is received a threaded stem 12 which extends from one end of the sleeve and carries a handle 1 3.

At the other end, the sleeve has a shnooth bore portion 14 in which there is positioned a locating bush 1 5 having an axial bore 1 6 coaxial with the passage 10 of the seating collar 9. The stem 12 has secured thereon a push rod 1 7 which is a close sliding fit within the bore 1 6 of the bush 1 5, say with a clearance of the order of 1-3 thousandths of an inch.

By rotation of the sleeve 6 relative to the body 1, its locating bush 1 5 can be moved axially towards and away from the seating collar 9. By rotation of the stem 1 2 relative to the sleeve 6, the push rod 1 7 can be moved axially along the bore 1 6 of the bush 1 5, and caused to protrude therefrom and to be axially withdrawn into the bush 1 5.

Referring now to figure 2, there is shown the positioning of some of the items prior to ejection of a chain pin.

A chain indicated generally at 1 8 has a link element 19 with side walls 20A, 20B mounted on sleeve 21 on which isjournalled a roller 22. Side walls 23A, 23B of a next link of the chain are coupled by a chain pin 24 which is a tight push fit in the walls 23A, 23B but is a clearance fit in the sleeve 21. The ends of the chain pin 24 protrude from each wall 23A, 23B by a small amount, say of the order of 1 millimeter in practice.

The chain has been positioned with one protruding end of the pin 24 engaged into the passage 10 of the seating collar 9. To facilitate this, the lip of the passage 10 is chamfered. The wall 23A of the chain link is butted up against the end of the seating collar 9. The other end of the pin 24 is engaged into bore 1 6 of the locating bush 1 5, and to facilitate this the lip of the bore 1 6 is chamfered. The wall 23B of the chain link is butted up against the end face of the locating bush 1 5. The tight axial engagement of the bush 15, the chain links, and the seating collar 9 is obtained by rotating the sleeve 6 in the appropriate direction by hand or by use of a tool engaging a nut 7 which is rigidly mounted on the sleeve for rotation therewith.The stem 12 is then rotated in the appropriate direction, by use of the handle 13, causing the push rod 1 8 to abut the end of the pin 24 and, with continuing movement, to thrust the pin 24 axially to the right in fig. 2 until the pin has been completely ejected frqm the links and has passed wholly into the end through the seating collar 9. The chain links are nevertheless stili retained in their same relative position, because they are clamped between the' sleeve 6 and the seating collar 9. The sleeve 6 can then be unlocked, and rotated in the reverse direction, to release the respective parts of the links which can then fall away from each other.

It will be appreciated that the invention is not restricted to the particular details described above but that numerous modifications and variations can be made without departing from the scope of the invention gs defined in the following Claims.

For example, the nut 7 can be replaced by a knurled knob forming part of, or rigidly mounted on, the sleeve 6.

Claims (4)

1. A chain pin extractor comprising a body having first and second opposed spaced portions, a seating of the first body portion having a bore opening at a radial abutment face opposed to the second body portion, a sleeve movable axially in the second body portion towards and away from the first body portion, and having one end portion nearer the first body portion provided with a coaxial bore opening at a radial abutment face opposed to the first body portion, and a stem movable axially in the sleeve and carrying a push rod which is a close-tolerance sliding fit in the bore of the sleeve.

2. A chain pin extractor, as claimed in claim 1, wherein the coaxial bore and radial abutment face of the sleeve are provided on a locating bushing forming an insert in the sleeve.

3. A chain pin extractor, as claimed in either of claims 1 and 2, wherein the bore and radial abutment face of the seating are provided on a seating collar which is inserted in an opening of the first portion of the body.

4. A chain pin extractor substantially as described herein with reference to the accompanying drawings.