NZ548849A - Trailer reversing coupling - Google Patents

Abstract

A master braking cylinder for use in a trailer braking system is disclosed. The cylinder includes a brake fluid reservoir (1) and piston (5) within a cylindrical chamber (2), with the piston able to be moved axially by an actuator (6) that projects from the chamber. Pressure applied by the actuator to the piston forces brake fluid through a brake line (7) to apply pressure to wheel braking in use. An equalising passage (3) from the reservoir can be closed off by a closure means (4) when the brake fluid in the chamber is being compressed, and opened when the fluid is not compressed, allowing fluid from the reservoir to flow into the chamber when necessary. The closure means can be disabled by an electromagnetic solenoid, opening the equalising passage. The remote activation allows the braking system to be disabled, for example, when the trailer is being reversed.

Description

FORM 5 S 9 Reg. 19(4) Fee: $250.00 NEW ZEALAND 111 ill mil IIII mil III! HI Hill I'm *10052289581* 2062080JAB 4 8 8 4 9 PATENTS ACT 1953 Insert number of Provisional Specifications) (if any) and date(s) of filing; otherwise leave blank Number: Date: Insert Title of TRAILER REVERSING COUPLING Invention COMPLETE SPECIFICATION ^sSaddresTand" '• T,M0THY EDWARD JOHN SIMPKIN, a New Zealand citizen, of nauonaiityof(each) 13 River Road, Dargaville, Northland, New Zealand applicant hereby declare the invention for which I pray that a patent may be granted to me and the method by which it is to be performed, to be particularly described in and by the following statement- indicate if following page is numbered "1a" ,pOA£ °' AUe200s 1 This invention relates to an improved master cylinder which has been adapted for use on a trailer braking system.

Many trailer braking systems rely on a sliding motion between the towing hitch on the trailer, which connects to the towing vehicle, and the frame of the trailer to cause actuation of a braking system when the trailer tries to overrun a braking or slowing towing vehicle. In those circumstances the towing hitch moves back with respect to the trailer frame causing a similar longitudinal movement of a pushrod forming part of a master cylinder arrangement, from which brake fluid under pressure is fed through suitable brake lines to the wheels to be braked via usual means such as drum brakes or disc brakes.

The problem which arises with this type of braking system is that when the driver wishes to reverse the trailer the towing hitch will, in many situations, move closer towards the centre of the trailer frame, causing the braked wheels to brake or lock up, making the trailer difficult or impossible to move. This problem is usually overcome by a mechanical device which prevents the sliding motion of the towing hitch with respect to the trailer frame occurring. When the device is actuated the master cylinder cannot be actuated and the brakes cannot be applied.

Unfortunately the actuation of such a device requires the driver to alight from the towing vehicle to put the device in place and also the driver must alight when the driver requires it to be disengaged. Frequently a driver can forget to do so and might then be unwittingly towing an unbraked trailer.

Furthermore the actuation of the device into an engaged or a disengaged position is not always easy if the trailer is, at the time, pushing on the towing vehicle.

The present invention was devised in order to provide a solution to the above-mentioned problems or to at least give the public a useful choice.

The present invention consists in a trailer master cylinder having a reservoir for brake fluid, a piston housing with a cylindrical internal chamber, a piston within the cylindrical internal chamber, a piston actuation means projecting from the piston housing adapted in use to be moved to cause axial movement of the piston, an outlet from the internal chamber allowing a brake line to be connected thereto in use to enable pressure applied via the piston actuation means and thus the piston to brake fluid in the internal chamber to be applied to wheel braking in use, an equalising passage from the reservoir, an equalising closure means adapted in normal use to close off the equalising passage when brake fluid within the internal chamber is being compressed and to open said equalising passage when the fluid is not compressed, allowing fluid from the reservoir to flow into the internal chamber when necessary, characterised in that the equalising closure means is able to be disabled via an electromagnetic solenoid, thus opening the equalising passage.

Disablement is possibly caused when a signal from a vehicle electrical system in use indicates that reverse gear has been selected and causes current to flow in the solenoid thus ensuring that the trailer brakes are inoperative when the towing vehicle is reversing the trailer. lINTELL^fuATpROpi^ OF N.Z. - 5 JUN 2007 HEcem/ed The present invention in a preferred form consists in a trailer master cylinder having a reservoir for brake fluid, a barrel with a cylindrical internal chamber communicating at an otherwise closed end with said reservoir via an aperture therein, a piston within the barrel, a piston rod projecting from the barrel adapted in use to be moved in a longitudinal direction into or out of the barrel, thus driving the piston, an equalising closure means adapted to close off the aperture through the closed end of the barrel when brake fluid within the barrel is being compressed and to open said aperture when the fluid is not compressed, allowing fluid from the reservoir to flow into the chamber when necessary, an outlet from the chamber allowing a brake line to be connected thereto in use to enable pressure applied to the brake fluid in the barrel to be applied to wheel braking in use, characterised in that there is a plunger which passes through said aperture, while yet allowing fluid to flow through said aperture and is capable in use of contacting the closure means to push it towards the piston, thus opening said aperture, a gland through the wall of the reservoir through which the plunger slidably passes, and an electromagnetic solenoid adapted when energised to drive the plunger to cause the closure means to open said aperture.

Such energising might be when a signal from the towing vehicle electrical system, in use, indicates that reverse gear has been selected, thus ensuring that the brakes are inoperative when the towing vehicle is reversing the trailer.

Preferably the solenoid comprises a coil coaxial with the plunger actuating a magnetically permeable member to which the plunger is attached for axial sliding movement within suitable bearing means which are sealed at the outer end of the coil to prevent loss of brake fluid. 4 INTELLECTUAL PROPERTY OFFICE OF N.7 - 5 2007 RECEIVEC Preferably the plunger is slidable within a close fitting gland which is screwed into a threaded hole in the reservoir wall which is concentric with said first aperture.

Preferably the plunger is fastened to a steel core which slides in a brass housing inside the coil.

Preferably the nose of the core adjacent the plunger is tapered and is able to be driven against a tapered depth stop seat forming part of the coil housing when the electromagnetnet is activated.

Preferably the periphery of the brass housing extends beyond the wall of the core and is closed at that end.

Preferably the plunger and the core are adapted to be lubricated by brake fluid.

Preferably the electromagnet windings are encapsulated within a spool which in turn is enclosed within a steel shroud.

INTELLECTUAL HOPfcRTY OFFICE OF N.Z. - 5 JUN 2007 RECE'VfP Preferred forms of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a somewhat schematic central longitudinal cross-sectional view through a preferred form of master cylinder adapted for use with a trailer and fitted with the improvement according to the present invention; Figure 2 shows a schematic form of the invention where the reservoir is perhaps physically separate from the piston housing except for communication via the equalising passage and equalising closure means is contained within the reservoir and actuated by an electromagnetic solenoid surrounding the equalising passage; Figure 3 shows a schematic form of the invention where the reservoir is perhaps physically separate from the piston housing except for the communication via the equalising passage and equalising closure means is contained within the reservoir and actuated by an electromagnetic solenoid also contained within the reservoir; Figure 4 shows a variation where the equalising passage is teed off from the brake line outlet from the cylindrical chamber and the equalising closure means is contained within the equalising passage and is actuated by an electromagnetic solenoid whose plunger sealingly passes through the wall of the brake line outlet; Figure 5 shows a variation where the electromagnetic coil surrounds the cylindrical internal chamber while the equalising passage from the reservoir comprises an axial aperture through an end wall of the cylindrical internal chamber (which is the predominant position for prior art trailer master cylinders); Figure 6 shows a variation of Figure 2 where the actuating solenoid is also outside of the reservoir; and Figure 7 shows a variation of Figure 4 where the solenoid is interposed between the brake line outlet and the reservoir.

Referring first of all to Figure 1, the master cylinder would usually be cast, perhaps in aluminium, and has a reservoir 1 and a barrel 2. The reservoir is adapted to contain brake fluid as is the barrel and there is communication from the reservoir to the barrel via aperture 3. The aperture 3 is in some circumstances closed by closure 4. The piston 5 slidable within the cylindrical chamber within the barrel is actuated by means of a pushrod 6 which is adapted to be moved lengthwise with respect to the cylindrical barrel, thus causing the piston 5 to compress the brake fluid when the trailer exerts a pushing force onto the towing vehicle.

In normal use, brake fluid which is compressed passes through the passage 7 into a brake line outlet comprising a female threaded boss 8 to which the brake line can be attached. There is a threaded hole 9 in the reservoir wall concentric with the aperture 3. A gland 10 is screwed in a leakproof manner into hole 9. A plunger 11 is generally cylindrical perhaps of 5mm diameter except at the end which is adapted to pass through the aperture 3 where it might be triangulated (not shown) to provide improved clearance for the flow of brake fluid through the aperture 3 when needed. The gland includes a gripping portion 12 which might have flats on it enabling the gland to be rotated by an open-ended spanner and it is also integral with a flange 13 which has a male thread 25 around its periphery. The gland 10 is magnetically conductive and thus would usually be formed of steel. There is also a conical seat 14 and a short female threaded portion 15 within the flange.

A non-magnetically conductive housing sleeve such as a brass sleeve 16 is adapted to threadedly engage with the thread 15, having a male thread at its inner end while at its outer end it is closed at 17.

Overlying the sleeve 16 is a spool 18 which may be made of a plastics material and the spool contains the windings 19 of an electromagnetnet, the feed wires for which (not shown) pass through suitably sealed apertures (not shown) in the flange 13.

The plunger 11 is fitted e.g. by means of a press fit, into the magnetically conductive core 20 which may be a steel core, provided with a tapered nose 21 adapted to mate with and seat against the conical taper 14, forming a depth stop and plunger centering means under some conditions of use. There is a slight difference in the taper angles to facilitate unseating against magnetic forces. The opposite end of the core 20 is restricted in its outward travel by the closed end 17. In practice brake fluid may optionally be able to pass through the gland to lubricate the peripheries of the plunger 11 and the core 20.

The spool is enclosed by a magnetically permeable shroud comprising a cylinder 23 which is threaded onto threads 25 and an annular end 24 which completes the magnetic circuit. When power is applied to the coil, such as when the vehicle is put into reverse, and there is a suitable connection between the electrical coupling between the towing vehicle and the trailer to convey the voltage normally intended for the trailer's reversing light (which most trailers do not have) to the coil which is also connected to the vehicle earthing system, the core 20 tries to centralise within the coil and is rammed towards the master cylinder with the conical seat 14 and conical nose 21 limiting the travel and maintaining alignment of the plunger 11 within the gland 10. The closure 4 is forced away from the aperture 3 and thus force applied to the piston 5 as the towing vehicle reverses does not cause any undue rise in the pressure of the brake fluid within the barrel 2. Instead the brake fluid is ejected through the aperture 3 into the reservoir which is made of a suitable size, or is initially filled with a suitable quantity of brake fluid to allow that to happen. When the vehicle is taken out of reverse then the coil 14 is de-activated and the usual compression spring 25 will cause the closure 4 to push the plunger 11 back into the gland 10 or that will at least occur when normal braking, i.e. not reverse braking, next occurs.

While the plunger is described passing through the aperture 3 there could be a second aperture, displaced from the first, through which the plunger passes to press on the closure 4.

Thus a simple and neat system is provided which is entirely automatic in operation not requiring the vehicle driver to leave the vehicle to engage or disengage a manual lock when the trailer is to be, or has been, reversed.

It also has two major advantages: first of all because the mechanism is entirely automatic it will always be functional, whereas with a manual device it is all too easy for a driver to leave it in reverse mode when in fact the vehicle is being driven forward, in which case the trailer has no operative brakes. Also the device can be constructed to have sufficient power that even when a trailer to be reversed is pushing against the towing vehicle prior to reverse gear being selected and thus even when the closure is being pushed to seal the aperture 3 the force exerted by the coil 19 is sufficient to dislodge the closure 4 from the aperture 3, relieving that pressure.

Variations of the preferred concept are shown in Figures 2 to 7 which are purely schematic and which will be largely self-explanatory. The piston housing, while it needs to contain a cylindrical internal chamber for the piston, can be of any external shape. The actuation means which projects from the piston housing need not necessarily be a straight rod projecting out an end, but could be a cranked or pivoted leverage system. The equalising passage may not be a simple aperture such as aperture 3 of Figure 1 but could be a relatively long passage such as passage 33 of Figure 3 or 63 of Figure 6 or a passage teed off the brake line outlet such as passage 43 of Figure 4 or 73 of Figure 7 or 83 of Figure 2.

In the Figures no attempt has been made to accurately depict the means which would normally be present to cause the equalising closure means such as 34, 44, 54, 64, 74 and 84 to be adapted to close off the equalising passage when required under normal braking. Such means might usually comprise light springs. Also, no attempt has been made to illustrate the precise connection between the equalising closure means and the plunger or armature of the solenoid.

It will also be understood that in some cases the current required for the electromagnet may be greater than can be handled through the normal vehicle wiring system to its reversing light(s) which wiring is also coupled to a female outlet capable of receiving a trailer plug. In such a case provision can be made for the selection of reverse gear on the vehicle to actuate a relay connected to the trailer electromagnet via wiring of suitable capacity. Such a relay would probably be located on the towing vehicle as a special run of wiring to and from the relay would possibly be necessary via a suitable connecting plug to the trailer to handle a large current. An alternative is to have a simple manual switch to actuate the solenoid but that would not be as fail safe as the above type.

Claims (4)

WHAT I CLAIM IS:

1. A trailer master cylinder having a reservoir for brake fluid, a piston housing with a cylindrical internal chamber, a piston within the cylindrical internal chamber, a piston actuation means projecting from the piston housing adapted in use to be moved to cause axial movement of the piston, an outlet from the internal chamber allowing a *;brake line to be connected thereto in use to enable pressure applied via the piston actuation means and thus the piston to brake fluid in the internal chamber to be applied to wheel braking in use, an equalising passage from the reservoir, an equalising closure means adapted in normal use to close off the equalising passage when brake fluid within the internal chamber is being compressed and to open said equalising passage when the fluid is not compressed, allowing fluid from the reservoir to flow into the internal chamber when necessary, characterised in that the equalising closure means is able to be disabled via an electromagnetic solenoid, thus opening the equalising passage.;

2. A trailer master cylinder having a reservoir for brake fluid, a barrel with a cylindrical internal chamber communicating at an otherwise closed end with said reservoir via an aperture therein, a piston within the barrel, a piston rod projecting from the barrel adapted in use to be moved in a longitudinal direction into or out of the barrel, thus driving the piston, an equalising closure means adapted to close off the aperture through the closed end of the barrel when brake fluid within the barrel is being compressed and to open said aperture when the fluid is not compressed, allowing fluid from the reservoir to flow into the chamber when necessary, an outlet from the chamber allowing a brake line to be connected thereto in use to enable;pressure applied to the brake fluid in the barrel to be applied to wheel braking in use, characterised in that there is a plunger which passes through said aperture, while yet allowing fluid to flow through said aperture and is capable in use of contacting the closure means to push it towards the piston, thus opening said aperture, a gland through the wall of the reservoir through which the plunger slidably passes, and an electromagnetic solenoid adapted when energised to drive the plunger to cause the closure means to open said aperture.;

3. A trailer master cylinder having a reservoir for brake fluid, a barrel with a cylindrical internal chamber communicating at an otherwise closed end with said reservoir via a first aperture therein, a piston within the barrel, a piston rod projecting from the barrel adapted in use to be moved in a longitudinal direction into or out of the barrel, thus driving the piston, an equalising closure means adapted to close off said first aperture through the closed end of the barrel when brake fluid within the barrel is being compressed and to open said first aperture when the fluid is not compressed, allowing fluid from the reservoir to flow into the chamber when necessary, an outlet from the chamber allowing a brake line to be connected thereto in use to enable pressure applied to the brake fluid in the barrel to be applied to wheel braking in use, characterised in that there is a plunger which passes through a second aperture in said closed end, and is capable of contacting the closure means to push it towards the piston, thus opening said first aperture so that in use, if the piston is moved towards the closure means, braking pressure is not applied to the wheels but instead the brake fluid which is compressed flows back into the reservoir, a sealing gland through said closed end through which the plunger slidably but sealingly passes, and iNftLLtUlUAL ► HUPfcMY OFFICE OF N.Z.;13 - 5 JUN 2007;RECEIVED;an electromagnetic solenoid adapted when energised to drive the plunger to cause the closure means to open said aperture.;

4. A trailer master cylinder substantially as herein described with reference to the accompanying drawings.;C, Gshorn* TIMOTHY EDWARD JOHN SIMPKIN By his authorised agents J.D. HARDIE & CO. 14 liM ffcLLtU I UAL ^'HUPtHTY OFFICE OF N.Z. - 5 JUN 2007 RECEIVED