GB2410207A

GB2410207A - Coupling device

Info

Publication number: GB2410207A
Application number: GB0401429A
Authority: GB
Inventors: Anthony Charles Rust Smith
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-01-23
Filing date: 2004-01-23
Publication date: 2005-07-27
Anticipated expiration: 2024-01-23
Also published as: WO2005070621A1; GB0401429D0; GB2410207B

Abstract

A coupling device 10 for transmitting a torque from a torque input member to a torque output member, the device comprising a plunger 12, an elongate body 14 in which the plunger 12 is movable between retracted and extended positions, and screw means 16 disposed in the body and operable to move the plunge 12 between the retracted and extended positions, the body 14 having coupling means 38 for coupling to one of the torque members, the plunger 12 having coupling means 28 for coupling to the other torque member, and the plunger 12 having engagement means 24 that is engageable with a co-operating portion 32, 40 of the body so as substantially to prevent rotation of the plunger 12 relative to the body 14. The coupling device may be an extender bar 10 for attachment between a ratchet tool and a socket spanner, to enable access to a nut or bolt head in a confined space.

Description

241o2o7 C959.00/S TITLE: COUPLING DEVICE

Field of the Invention

This invention relates to a coupling device for transmitting a torque from a torque input member to a torque output member, and in particular to a coupling device for transmitting a torque from a ratchet tool to a socket spanner.

Background to the Invention

Socket sets comprising a ratchet tool, socket spanners of various sizes and extender bars of various lengths are well known. The extender bars of such a socket set are attachable between the ratchet tool and a socket spanner to enable the socket spanner to be used in a confined space, and might typically have lengths of 50mm, 150mm and 250mm.

It has been found that the design of modern cars is so compact that, when servicing such cars, it is often necessary to use an extender bar to gain access to a nut or bolt head, and also to operate the ratchet tool itself in a confined space. In that event, it often happens that the ava fable extender bars are just too long or short for the confined space.

To this end, 25mm extender bars are available, which can be used in combination with other extender bars, including such 25mm extender bars, to increase the length of the extender bar assembly in 25mm increments.

It is not possible to make a shorter such extender bar because of the minimum lengths required for the socket by which the extender bar is connected to the ratchet tool, and the stub by which a socket spanner is connected to the extender bar.

In order to address this shortcoming, an adjustable extender bar has been produced, which comprises an outer sleeve in which a core is slidable. The outer sleeve has a socket for attachment to a ratchet tool and the core has a stub for attachment to a socket spanner. The I outer sleeve is provided with a row of holes at approximately 15mm intervals and the core I has a spring-loaded ball bearing for engagement with the holes. The core can be slid between several positions in which the ball bearing engages with a hole, and the extender bar is therefore adjustable in length in 1 5mm increments.

It is presumably not possible to reduce the distances between the holes in the sleeve, and thus the increments by which the length of the extender bar is adjustable, without significantly weakening the sleeve.

Summary of the Invention

According to a first aspect of the invention there is provided a coupling device for transmitting a torque from a torque input member to a torque output member, the device comprising a plunger, an elongate body in which the plunger is movable between retracted and extended positions, and screw means disposed in the body and operable to move the plunger between the retracted and extended positions, the body having coupling means for coupling to one of the torque members, the plunger having coupling means for coupling to the other torque member, and the plunger having engagement means that is engageable with a co-operating portion of the body so as substantially to prevent rotation of the plunger relative to the body.

The invention therefore provides a coupling device the length of which is continuously and easily variable.

Preferably the coupling means of the body is a socket for coupling to a stub of a torque member.

Preferably the coupling means of the plunger is a stub for coupling to a socket of a torque member.

In a preferred embodiment of the invention the coupling device is an extender bar, the coupling means of the body being a socket for coupling to a stub of a ratchet tool and the coupling means of the plunger being a stub for coupling to a socket of a socket spanner.

Typically the stub of the plunger would be provided with a spring-loaded ball bearing for engagement with a notch in a socket of a socket spanner, so as to retain the stub in couplement with the socket spanner.

The engagement means of the plunger may advantageously be an external surface of the plunger.

The co-operating portion of the body may advantageously be an internal surface of the body.

The plunger preferably has a portion of polygonal cross section for engagement with the internal surface of the body.

More preferably still, the plunger has a portion of hexagonal cross section for engagement with the internal surface of the body.

The portion of hexagonal cross section enables a torque to be applied to the plunger by means of a suitably sized spanner engaged with the portion of hexagonal cross section.

The plunger may advantageously also have an intermediate portion between the portion of polygonal cross section and the coupling means, the intermediate portion having a smaller cross-sectional area than the portion of polygonal cross section.

The intermediate portion enables a ring spanner to be disengaged from the portion of hexagonal cross section without the need for disengaging the plunger from the torque member.

This is useful, for example, where a ring spanner has been used to turn the plunger to turn a socket spanner to loosen a nut or bolt to finger tightness, and it is desired to remove the nut or bolt by turning the body with one's fingers, rather than by means of the ring spanner.

In the preferred embodiment the intermediate portion is of cylindrical cross section, the cylindrical cross section providing mechanical strength whilst enabling the plunger to be rotated inside the ring of a ring spanner.

The body, plunger and/or screw means may advantageously be provided with a stop to define the extended position of the plunger relative to the body.

Preferably, however, the plunger is provided with indicator means for indicating when the plunger is in a furthest recommended extended position relative to the body.

In the preferred embodiment the portion of polygonal cross section of the plunger is formed with notches towards its distal end, which notches are concealed by the body when the plunger is in the retracted position, and visible when the plunger is in a furthest recommended extended position relative to the body.

The notches provide an indication of the furthest recommended extension of the plunger relative to the body, whilst allowing the plunger to be removed from the body, for example for oiling or cleaning of the coupling device.

The body may advantageously be generally cylindrical and define a generally polygonal cavity for receiving the plunger.

Preferably the body defines a generally hexagonal cavity for receiving the plunger.

In the preferred embodiment the body defines a cavity in the form of a hexagon, the apices of which are marginally enlarged.

This ensures that, when a torque is applied to the body, there is a slight rotation of the body relative to the plunger, such that the flats of the portion of hexagonal cross section of the plunger, as opposed to the apices, engage with the internal surface of the body, thus reducing the shear stress to which the plunger is subjected in use.

Thus the object of the invention may be achieved by an embodiment of the coupling device of which the plunger has engagement means that is engageable with a co-operating portion of the body so as substantially to prevent rotation of the plunger relative to the body.

The body may advantageously be provided with purchase means to enable the body to be turned with one's fingers.

In the preferred embodiment the purchase means is a splined portion.

In the preferred embodiment the screw means is a screw, the head of which is accessible through the socket of the body, which is retained in the body by a lock nut, and the shank of which is engageable with an axial tapped bore in the plunger.

The tapped bore is preferably formed centrally in the plunger. This has the advantage that, when the plunger is subjected to case-hardening, for example by cyanide-hardening, the molten sodium cyanide penetrates the tapped bore and the plunger is thereby hardened both from the outside inwards and from the inside outwards.

Brief Description of the Drawings

The invention will now be described, by way of example, with reference to the attached drawing figures in which: Figure 1 is a sectional view of a coupling device in accordance with the invention; Figure 2 is a perspective view of the coupling device of Figure 1; and Figure 3 is a perspective view of the plunger of the coupling device of Figures 1 and 2.

Detailed Description of an Embodiment

The coupling device of Figure is in the form of an extender bar 10 comprising a plunger indicated generally by reference numeral 12, a body indicated generally by reference numeral 14 and a screw means in the form of a screw indicated generally by reference numeral 16.

The plunger 12 consists of an elongate case-hardened chromium-vanadium steel forging indicated generally by reference numeral 18, a helical compression spring 20 and a ball bearing 22.

The forging 18 has engagement means in the form of a base portion 24 that is of regular hexagonal cross section, and also has a cylindrical intermediate portion 26 and coupling means in the form of a stub 28 that is of square cross section for coupling to a socket of a torque output member in the form of a socket spanner (not shown), or another extension bar (not shown). The spring 20 and ball bearing 22 are retained in a hole 23 drilled in one of the four side faces of the stub 28, the spring serving to urge the ball bearing out of the hole and the mouth of the hole being narrowed using a punch so as to retain the ball bearing.

When the stub is coupled to a socket of another component, the ball bearing is urged by the spring into a notch inside the socket, so as to keep the stub in couplement to the socket.

The forging 18 has a central axial tapped hole 30, sized to receive an MS thread of 0.8mm pitch, that is to say, one revolution of the thread will advance the thread by 0.8mm along the hole.

The hole 30 continues for the entire length of the base portion 24 and for most of the intermediate portion 26, ending just before the stub 28.

The hole 30 in the base and intermediate portions and the hole 23 in the stub are formed, the spring 20 and ball bearing 22 are placed into the hole 23 and the hole narrowed before the plunger is case-hardened by cyanide dipping. This enables the molten sodium cyanide used in the dipping process to penetrate the holes 23 and 30 so as to harden the cores of the base and intermediate portions 24 and 26 and the core of the stub 28.

In addition to simplifying the machining of the plunger (which would otherwise involve machining hardened steel), case-hardening of the plunger both from the outside of the plunger inwards and from the inside of the plunger outwards greatly increases the mechanical strength of the plunger.

The body 14 is generally cylindrical, made of case-hardened chromiumvanadium steel and consists of a wide portion 32, purchase means in the form of a splined portion 34, and a narrow portion 36. The narrow portion 36 and splined portion 34 define coupling means in the form of a square socket 38 for coupling to a stub of a torque input member in the form of a ratchet tool (not shown) and the wide portion 32 defines a co-operating portion in the form of a generally hexagonal cavity 40 with which the hexagonal base portion of the plunger is engageable. The socket 38 and cavity 40 are substantially separated by a partition 42, however a central hole in the partition 42 links the socket 38 and cavity 40. The central hole is sized to receive the shank of an M5 screw.

The screw 16 is a hardened chromium-molybdenum steel M5 screw with an 0. 8mm thread pitch for engagement with the tapped hole 30 in the plunger 12. The screw is disposed in the body through a mild steel washer 44 such that the washer 44 abuts the partition 42 and the head 46 of the screw abuts the washer, the head 46 of the screw being accommodated in the square socket 38 and the shank 48 of the screw projecting through the hole in the partition into the generally hexagonal cavity 40.

The shank of the screw passes through a further mild steel washer 50, which abuts the opposite side of the partition to the washer 44, and the head 46 of the screw is maintained in abutment with the washer 44 by a lock nut 52 that is tightened onto the shank 48 of the screw into abutment with the washer 50. The head 46 of the screw has a cross-shaped slot enabling the screw to be turned relative to the body by means of a Phillips (TM) screwdriver.

The extender bar is assembled by introducing the hexagonal base portion 24 of the plunger 12 into the generally hexagonal cavity 40 of the body 14 until the shank of the screw 16 engages with the tapped hole 30 of the plunger. Clockwise rotation of the screw head 46 (as seen from above) relative to the body then draws the plunger into the body and anticlockwise rotation of the screw head drives the plunger out of the body.

Turning to Figure 2, the hexagonal base portion 24 of the plunger 12 and the splined portion 34 of the body 14 are more clearly visible.

The hexagonal cross section of the base portion 24 enables the plunger to be inserted into the ring of a suitably sized ring spanner, or a suitably sized open spanner to be placed over the plunger, and the extender bar to be turned using the spanner. This is useful where there is insufficient space to use a ratchet tool to turn the extender bar, or where it is desired to use a spanner that is longer than the ratchet tool to start a jammed nut or bolt.

Where a ring spanner is so used, the cylindrical intermediate portion 26 enables the ring spanner to be slid off the hexagonal base portion 24 and onto the intermediate portion 26, which can turn freely inside the ring of the ring spanner.

In this way the ring spanner can be disengaged from the base portion of the plunger once the nut or bolt is started, and the extender bar turned using the ratchet tool or one's fingers.

Where it is desired to turn the extender bar using one's fingers, the splined portion 34 of the body provides a purchase, which is valuable where the extender bar is used in oily or greasy conditions.

The generally hexagonal cavity of the body that accommodates and engages with the hexagonal base portion of the plunger has six parallel channels, one channel being formed at each apex of the hexagonal cavity.

The channels allow very slight rotation of the hexagonal base portion of the plunger relative to the hexagonal cavity in the body. This causes the body to transmit a torque from a ratchet tool to the base portion of the plunger predominantly through the flats of the base portion, rather than through its apices. This greatly reduces the shear stress on the apices of the base portion of the plunger, and enables the extender bar to be used to transmit greater torques than would otherwise be possible.

Turning to Figure 3, this shows the entire plunger 12 and, in particular, the notches 52 that are formed in each of the apices of the base portion 24 distal from the stud 28.

The notches 52 become visible to a user of the extender bar only when the plunger has been moved to its maximum recommended extension relative to the body, which is when approximately 4mm of the base portion of the plunger is engaged with the body. Turning the screw 16 anticlockwise after the notches 52 become visible will further extend the plunger until the plunger is driven free of the body, which enables component parts of the extender bar to be cleaned and oiled.

It will be apparent that the above description relates only to one embodiment of the invention, and that the invention encompasses other embodiments as defined by the claims set out hereafter.

Claims

C959.00/S CLAIMS

1. A coupling device for transmitting a torque from a torque input member to a torque output member, the device comprising a plunger, an elongate body in which the plunger is movable between retracted and extended positions, and screw means disposed in the body and operable to move the plunger between the retracted and extended positions, the body having coupling means for coupling to one of the torque members, the plunger having coupling means for coupling to the other torque member, and the plunger having engagement means that is engageable with a co-operating portion of the body so as substantially to prevent rotation of the plunger relative to the body.

2. A coupling device according to claim 1, wherein the coupling means of the body is a socket for coupling to a stub of a torque member.

3. A coupling device according to claim 1 or 2, wherein the coupling means of the plunger is a stub for coupling to a socket of a torque member.

4. A coupling device according to claim 3 when dependent from claim 2, wherein the coupling device is an extender bar, the coupling means of the body being a socket for coupling to a stub of a ratchet tool and the coupling means of the plunger being a stub for coupling to a socket of a socket spanner.

5. A coupling device according to any preceding claim, wherein the engagement means of the plunger is an external surface of the plunger.

6. A coupling device according to any preceding claim, wherein the cooperating portion of the body is an internal surface of the body.

7. A coupling device according to claim 6 when dependent from claim 5, wherein the plunger has a portion of polygonal cross section for engagement with the internal surface of the body.

8. A coupling device according to claim 7, wherein the plunger has a portion of hexagonal cross section for engagement with the internal surface of the body.

9. A coupling device according to claim 7 or claim 8, wherein the plunger has an intermediate portion between the portion of polygonal cross section and the coupling means, the intermediate portion having a smaller cross-sectional area than the portion of polygonal cross section.

10. A coupling device according to claim 9, wherein the intermediate portion is of cylindrical cross section.

ll. A coupling device according to any of claims l to 10, wherein the body, plunger and/or screw means is provided with a stop to define the extended position of the plunger relative to the body.

12. A coupling device according to any of claims 1 to 10, wherein the plunger is provided with indicator means for indicating when the plunger is in a furthest recommended extended position relative to the body.

13. A coupling device according to claim 12, wherein the portion of polygonal cross section of the plunger is formed with notches towards its distal end, which notches are concealed by the body when the plunger is in the retracted position, and visible when the plunger is in a furthest recommended extended position relative to the body.

14. A coupling device according to any preceding claim, wherein the body is generally cylindrical and defines a generally polygonal cavity for receiving the plunger.

15. A coupling device according to claim 14, wherein the body defines a generally hexagonal cavity for receiving the plunger.

16. A coupling device according to claim 15, wherein the body defines a cavity in the form of a hexagon, the apices of which are enlarged.

17. A coupling device according to any preceding claim, wherein the body is provided with purchase means to enable the body to be turned by the fingers of a user of the device.

18. A coupling device according to claim]7, wherein the purchase means is a splined portion.

l9. A coupling device according to claim 2 or any claim dependent therefrom, wherein the screw means is a screw, the head of which is accessible through the socket of the body, which is retained in the body by a lock nut, and the shank of which is engageable with an axial tapped bore in the plunger.

20. A coupling device according to claim l9, wherein the tapped bore is formed centrally in the plunger.

21. A coupling device substantially as hereinbefore described and with reference to the accompanying drawings.