GB1583548A - Coupling device for a fuel control mechanism - Google Patents

Description

(54) A COUPLING DEVICE FOR A FUEL CONTROL MECHANISM (71) We, LUCAS INDUSTRIES LIMITED, of Great King Street, Birmingham B19 2XF, a British Company, and the SEC RETARY OF STATE FOR TRANSPORT, of 2 Marsham Street, London SW1P 3EB, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - This invention relates to a coupling device for a fuel control mechanism and is particularly intended for use in a speed limiting system for a road vehicle, such as a motorised pedal cycle.

A coupling device, according to the invention, comprises a casing, an electromagnet winding mounted within the casing, first and second armatures associated with the electromagnet winding and movably mounted in the casing, a first drive element movable by said first armature and extending from said casing for connection to the fuel demand adjustment of the fuel control mechanism, and a second drive element movable by the second armature and extending from the casing for connection to the fuel supply adjustment of the fuel control mechanism, the armatures being arranged to be magnetically coupled when the winding is energised so as to transmit movement of the first drive element to the second drive element, but being magnetically uncoupled when the winding is de-energised.

Preferably, the armatures are slidably received within an elongated non-magnetic guide sleeve around which said winding extends and are movable linearly relative to the sleeve to transmit movement of the first drive element to the second drive element.

Preferably, said armatures include respective end surfaces which, when said winding is energised, are magnetically held in abutment to drivingly couple the armatures, de-energisation of the winding serving to release said surfaces so that said first armature is movable relative to the second armature.

Conveniently, said second armature is movable away from the first armature, when the winding is de-energised, to an inoperative position in which said end surfaces are spaced from one another.

Conveniently, a fixed stop is provided to define said inoperative position of the second armature.

Alternatively, resilient means acts on the second armature and is operable, when the winding is de-energised to urge the second armature against a fixed abutment.

Conveniently, one of said first and second armatures is formed with a bore in which at least part of the other armature is slidably received.

Preferably, said drive elements are adapted to replace a road vehicle throttle cable.

In a further aspect, the invention resides in a speed limiting system for a road vehicle comprising a coupling device as described in the preceding paragraphs and speed sensitive means operable to deenergise said winding in response to the vehicle road speed reaching a predetermined value.

Preferably, said speed sensitive means includes a centrifugal switch having a rotatable member adapted to be coupled to a vehicle member which is driven at a speed dependent on the vehicle road speed.

Preferably, said member is the vehicle speedometer.

In the accompanying drawings: - Figure 1 is a sectional view of a coupling device according to a first example of the invention; Figure 2 is a sectional view of a speed sensitive device for use in a speed limiting system employing the coupling device of Figure 1; Figure 3 is a sectional view of a speed sensitive device according to a modification of the first example.

Figure 4 is a diagrammatic illustration of a coupling device according to a second example of the invention; Figure 5 is a diagrammatic illustration of a coupling device according to a third example of the invention, and Figure 6 is an enlarged sectional view of part of a modification of the third example.

Referring to Figures 1 and 2, the coupling device of the first example forms part of a speed limiting system for a motorised pedal cycle of the kind which is driven by an internal combustion engine and in which the fuel supply to the engine is controlled by a carburettor. The purpose of the system is to limit the maximum road speed of the cycle by preventing the control valve of the carburettor being opened to increase the supply of fuel and air to the cycle engine when the road speed of the cycle has a predetermined maximum value, normally 30 m.p.h.

As shown in Figure 1, the coupling device includes a stepped cylindrical casing 11, which, in use, is fixed to the frame of the cycle and which is defined by a sleeve 12 having respective hollow, flanged pole pieces 13 secured to its opposite ends. The sleeve 12 and pole pieces 13 are formed of E.N. 2A steel and trapped between the pole pieces 13 is a synthetic resin former 14.

Carried by the former 14 is an electromagnet winding 15 which extends around the central portion of a brass tube 16 mounted in the bore in the casing 11.

Slidably received within the sleeve 16 are first and second cylindrical armatures 17, 18 respectively which are again formed of E.N. 2A steel and which each has a cable anchor 19 screwed into its outer end. In screw-threaded engagement with the inner end of the armature 17 is an axially extending pin 21 which is formed with an enlarged head portion 22 at its free end.

The head portion 22 is slidably received in a bore 23 extending through the armature 18, but is prevented from removal from the bore by an inwardly directed flange 24 formed at the inner end of the bore. Thus the armatures 17, 18 are capable of limited relative axial movement by an amount determined by the distance between the inner end of the armature 17 and the head portion 22 of the pin 21.

At its outer end, each pole piece 13 is externally screw-threaded and is in meshing engagement with an internally screwthreaded collar 25 so that an O-ring seal 26 is trapped between the collar and an external shoulder of the pole piece. One of the collars 25 also serves to compress a spring 27 against the armature 18 while the other collar 25 traps a stepped brass washer 28 against its associated pole piece 13 so that the washer 28 lies in the path of movement of the armature 17. Extending from the collars 25 are respective Bowden-type cables 29, 31 which each has one end of its fixed outer sleeve part secured to the associated collar 25 by means of a shrink fitted sleeve 32 while said one end of the inner flexible wire part of each cable extends through its associated collar and carries a brass boss 33.Each boss 33 is located at the outer end of a channel 34 formed in the adjacent anchor 19 with the channel 34 being stepped inwardly at said outer end so as to prevent the boss being axially withdrawn from the anchor. Thus, each loss 33 prevents relative movement between the inner wire part of its associated cable 29, 31 and the respective armature 17, 18 in a direction to separate the armatures.

At its opposite end, the inner wire part of the cable 29 is adapted to be connected to the carburettor valve of the associated pedal cycle, while the opposite end of the inner wire part of the cable 31 is adapted to be connected to the manually operable fuel demand adjustment of the cycle. Thus the device shown in Figure 1 is intended to be mounted on a pedal cycle in place of the existing throttle cable of the cycle.

In use, when the system shown in Figures 1 and 2 is mounted on a pedal cycle, energisation of the electromagnet winding 15 serves to retain the armatures 17, 18 in endto-end abutment. Then, when the rider of the cycle operates his fuel demand adjustment to increase or decrease the speed of the cycle, the movement thereby imparted to the inner wire part of the cable 31 is transmitted to the inner wire part of the cable 29 to adjust the position of the carburettor valve. Thus, in this situation, the fuel control of the cycle operates normally, it being appreciated that the movement of the armatures 18, 19 associated with a demand for an increase in speed is opposed by the spring 27 and the spring (not shown) associated with the carburettor valve.

When, however, the road sneed of the cycle reaches the predetermined maximum value, the speed sensor shown in Figure 2 and described in detail below is arranged to produce an output signal which is employed in any convenient manner to deenergise the winding 15. The armature 17 is thereby no longer held in abutment with the armature 18 and is urged by the carburettor spring away from the armature 18 until it is prevented from further movement by engagement with the washer 28 or by abutment of the head portion 22 with the flange 24, depending on the existing position of the throttle. In this way the inner wire part of the cable 29 is moved to either completely close the carburettor valve or return the valve to an idling position so that the supply of fuel and air to the engine is prevented or decreased respectively and the road speed of the vehicle is controlled.

Moreover, when the winding 15 is deenergised with the throttle only partly open, any attempt by the rider of the cycle to demand more speed has no effect since the armature 18 is no longer magnetically coupled to the armature 17 and hence merely slides along the pin 21.

When the road speed of the cycle falls below the predetermined maximum value, the speed sensor of the system again allows the winding 15 to energise so that the rider can regain control of the fuel supply to the engine. This may, however, necessitate the rider initially throttling back so as to move the armature 18 sufficiently close to the armature 17 for the latter to be urged by magnetic attraction back into abutment with the armature 18.

Turning now to Figure 2, the speed sensor of the system described above is in the form of a centrifugal switch adapted to be coupled to the existing speedometer drive cable 41 of the pedal cycle. The switch includes an insulating, synthetic resin base 42 formed integrally with an externally screw-threaded collar 43 which, in use, receives a lock nut 44 carried by the outer sheath of the drive cable 41, while the free end of the cable projects into the collar Riveted to the base 42 is a synthetic resin cover 45 formed at its end remote from the base 42 with an integral, internally screwthreaded boss 46 which, in use, is screwed into the rear of the speedometer head of the cycle. Rotatably mounted between the base 42 and the cover 45 is a spindle 47 which is formed of mild steel so as to be electrically conductive.At one end, the spindle 47 is hollow and carries a drive bush 48 having a square section bore which receives the free end of the speedometer cable 41, while at its other end the spindle 47 extends through the boss 46 and reproduces the shape of the cable 41 so as to provide the necessary connection to the drive mechanism of the speedometer head.

It will therefore be appreciated that the system shown can be readily coupled to the existing speedometer of a motorised pedal cycle by removing the speedometer drive cable from the speedometer head and then mounting the switch shown in Figure 2 between the end of the cable and the rear of the speedometer head.

Keyed to the spindle 47 is an insulating disc 49 which is formed of a glass-filled epoxy resin and is provided at its surface adjacent the base 42, with inner and outer annular, conductive tracks 51, 52 respectively. The inner track 51 is physically and electrically connected to the spindle 47, but is spaced from the outer track 52 by the insulating material of the disc 49. In sliding contact with the tracks 51, 52 are respective carbon brushes 53, each of which is mounted at one end of a respective conductive spring strip 54 while the other end of the spring strip is secured by means of a conductive rivet 55 to the base 42 and an external terminal 56.

Mounted on the surface of the disc 49 remote from the base 42 is a movable weight 57 formed of an electrically conductive material and a fixed counter-weight 58. The weight 57 is carried by a conductive arm 59 which at one end is pivotally mounted on a conductive post (not shown) which extends through the disc 49 and is electrically connected to the outer track 52.

Acting on the arm 59 is a spring 61 which normally urges the weight 57 into contact with a copper rivet 62 extending through the spindle 47. Thus an electrical circuit between the inner and outer tracks 51, 52 is normally completed by way of the spindle 47, the rivet 62, the weight 57, the arm 59 and the pivot post for the arm 59. When, however, the spindle 47 is rotated by the cable 41 the weight 57 is urged radially outwardly against the action of the spring 61 with a force dependent on the speed of rotation of the cable 41 and hence on the road speed of the associated pedal cycle.

The force with which the spring 61 opposes radial movement of the weight 57 is set so as to prevent movement of the weight 57 until the road speed of the cycle attains the desired maximum value. When, however, the maximum road speed is reached, centrifugal forces overcome the resilience of the spring 61 and hence the weight 57 moves radially outwardly under the control of a stop 63 so as to break the electrical circuit between the tracks 51, 52. In this way, the switch provides an output signal which is used to de-energise the winding 15.

Referring to Figure 3, in the modification shown therein the speed sensor is in the form of a centrifugal switch adapted to be coupled to the speedometer head of a pedal cycle in place of the existing speedometer drive cable. The switch includes a tubular casing 71 which is closed at its opposite ends by respective, insulating end caps 72. Rotatably mounted between the end caps 72 is a synthetic resin shaft 73 which carries at each of its opposite ends a respective drive bush 74. Each bush 74 is formed with a square-section bore and receives the complementarily shaped end portion of a respective drive cable 75 so that the shaft 73 is coupled to the cables 75. At their opposite ends, the cables 75 are adap ted to be connected between the speed ometer head of the pedal cycle and the front wheel speedometer drive.

Fixed to the shaft 73 adjacent its opposite ends are first and second carrier members 76, 77 respectively which support respective copper slip rings 78, 79. The slip rings present to their adjacent end caps 72 continuous, annular conductive surfaces which are engaged by respective carbon brushes 81 resiliently mounted in the insulating end caps 72. Secured to the carrier member 76 is one end of an elongated, conductive spring strip 82 which is soldered to the slip ring 78. The spring strip 82 extends along the shaft 73 and is arranged so that the opposite end of the strip is normally urged under its own resilience against a contact piece 83 carried by the member 77 and soldered to the slip ring 79. Thus the strip 82 normally completes an electrical circuit between the brushes 81 by way of the slip rings 78, 79.

Adjacent its opposite end, the spring strip 82 engages a ball 84 which is slidably mounted in a radially extending blind bore 85 formed in the shaft 73 and which is normally urged by the spring strip against the closed end of the bore. When, however, the shaft 73 is rotated, the ball 84 is urged radially outwardly against the resilient action of the spring strip 82 with a force dependent on the rotational speed of the cables 75 and hence on the road speed of the associated pedal cycle. Again, the arrangement is such that, when the road speed of the cycle attains the desired maximum value, the centrifugal forces acting on the ball 84 are sufficient to overcome the resilience of the spring strip 82 and hence the strip is moved out of engagement with the contact piece 83 so as to break the electrical circuit between the brushes 81.The carrier member 77 is located on the shaft 73 so as to partially overlap the bore 85 and thereby prevent complete withdrawal of the ball 84 from the bore 85.

Referring now to Figure 4, the coupling device of the second example includes a generally cylindrical casing 111 in which is secured a magnetic steel yoke 112 carrying a cylindrical, non-magnetic guide sleeve 113 extending coaxially with the casing 111.

Mounted on a former 114 so as to extend around the sleeve 113 is an electromagnet winding 115 and slidably received within the sleeve 113 are first and second solid, cylindrical, soft iron armatures 116, 117 respectively. At their outermost ends, the armatures 116, 117 are rigidly connected to the inner flexible wire parts of respective Bowden-type cables 118, 119 which extend from the casing 111 and have their fixed outer sleeve parts secured to the casing.

At its free end, the inner wire part of the cable 118 is adapted to be connected to the manually operable fuel demand system of the associated pedal cycle, while the free end of the inner wire part of the cable 119 is adapted to be connected to the carburettor valve of the cycle. Again, therefore, the device of the second example is intended to be mounted on a pedal cycle in place of the existing throttle cable of the cycle.

Mounted in a channel 122 in the yoke 112 is an L-shaped member 123 which is urged by a compression spring 124 towards the armature 117 so that one limb 123a of the member engages the outer end of the armature 117. The rating of the spring 124 is arranged to be greater than that of the carburettor spring alone but less than the sum of the ratings of the carburettor spring ard a compression spring 121 acting between the armature 116 and the adjacent end of the casing 111. Both the carburettor spring and the spring 121 act in the opposite direction to the spring 124 and hence, when the winding 115 is energised, the member 123 is urged to move with the armature 117 along the channel 122 as the rider of the cycle operates his fuel demand adjustment.The arrangement is, however, such that the other limb 123b of the member 123 engages one end of the channel 122 when the opening of the carburettor valve attains a predetermined value corresponding, on a level road, with the maximum predetermined road speed of the cycle. At this speed, of course, the winding 115 is deenergised so that the armature 117 is uncoupled from the armature 116 and only experiences the resilient action of the spring 124 and the carburettor spring. Thus the armature 117 is now urged by the greater force exerted by the spring 124 to remain in its existing position with the other limb 123b of the member 123 engaging said one end of the channel 122. Hence, with this construction, the rider of the cycle can be prevented from increasing the supply of fuel to the engine when the road speed of the cycle reaches the predetermined maximum value, without this being accompanied by the partial or complete closure of the carburettor valve.

Referring now to Figure 5, the device of the third example is similar in construction to that of the previous example, except that the member 123 and its associated spring 124 are now removed, while the armature 117 is now hollow so that the armature 116 is slidably received within the armature 117. With this arrangement, when the winding 115 is energised, the armature 116 abuts against the closed end of the armature 117 and, although the armature 117 drops into engagement with a fixed stop defined by the casing 111 when the winding 115 is de-energised, the armature 116 remains within the armature 117 in this inoperative position.

The modification of the third example shown in Figure 6 again employs a hollow armature 117 in which the armature 116 is slidably received, but now the armatures 116, 117 include co-operating stop means which define the inoperative position of the armature 117. The stop means is defined by a stepped bore 125 formed in one end of the armature 116 and a headed spigot 126 projecting into the bore 125 from the closed end of the armature 117. With this arrangement, it is found that when the armatures 116, 117 are uncoupled and the winding 115 is re-energised, engagement of the armatures 116, 117 is re-established automatically without the necessity for throttling back.

WHAT WE CLAIM IS: - 1. A coupling device for a fuel control mechanism, comprising a casing, an electromagnet winding mounted within the casing, first and second armatures associated with the electromagnet winding and movably mounted in the casing, a first drive element movable by said first armature and extending from said casing for connection to the fuel demand adjustment of the fuel control mechanism, and a second drive element movable by the second armature and extending from the casing for connection to the fuel supply adjustment of the fuel control mechanism, the armatures being arranged to be magnetically coupled when the winding is energised so as to transmit movement of the first drive element to the second drive element, but being magnetically uncoupled when the winding is de-energised.

2. A device as claimed in Claim 1, wherein the armatures are slidably received within an elongated non-magnetic guide sleeve around which said winding extends and are movable linearly relative to the sleeve to transmit movement of the first drive element to the second drive element.

3. A device as claimed in Claim 1 or Claim 2, wherein said armatures include respective end surfaces which, when said winding is energised, are magnetically held in abutment to drivingly couple said armatures, de-energisation of the winding serving to release said surfaces so that said first armature is movable relative to the second armature.

4. A device as claimed in Claim 3, wherein said second armature is movable away from the first armature, when the winding is de-energised, to an inoperative position in which said end surfaces are spaced from one another.

5. A device as claimed in Claim 1, and including a fixed stop for defining said inoperative position of the second armature.

6. A device as claimed in Claim 3, wherein resilient means acts on the second armature and is operable, when the winding is de-energised, to urge said second armature against a fixed abutment.

7. A device as claimed in any one of the preceding Claims, wherein one of said first and second armatures is formed with a bore in which at least part of the other armature is slidably received.

8. A device as claimed in any one of the preceding claims, wherein said drive elements are adapted to replace a road vehicle throttle cable.

9. A coupling device for a fuel control mechanism comprising the combination and arrangement of parts substantially as hereinbefore described with reference to and as shown in, Figure 1, or any one of Figures 4 to 6 of the accompanying drawings.

10. A speed limiting system for a road vehicle including a coupling device as claimed in any one of the preceding claims and speed sensitive means operable to deenergise said winding in response to the vehicle road speed reaching a predetermined value.

11. A system as claimed in Claim 10, wherein said speed sensitive means includes a centrifugal switch having a rotatable member adapted to be coupled to a vehicle member which is driven at a speed dependent on the vehicle road speed.

12. A system as claimed in Claim 11, wherein said member is the vehicle speedometer.

13. A speed limiting system comprising the combination and arrangement of parts substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. armature 117 drops into engagement with a fixed stop defined by the casing 111 when the winding 115 is de-energised, the armature 116 remains within the armature 117 in this inoperative position. The modification of the third example shown in Figure 6 again employs a hollow armature 117 in which the armature 116 is slidably received, but now the armatures 116, 117 include co-operating stop means which define the inoperative position of the armature 117. The stop means is defined by a stepped bore 125 formed in one end of the armature 116 and a headed spigot 126 projecting into the bore 125 from the closed end of the armature 117. With this arrangement, it is found that when the armatures 116, 117 are uncoupled and the winding 115 is re-energised, engagement of the armatures 116, 117 is re-established automatically without the necessity for throttling back. WHAT WE CLAIM IS: -

1. A coupling device for a fuel control mechanism, comprising a casing, an electromagnet winding mounted within the casing, first and second armatures associated with the electromagnet winding and movably mounted in the casing, a first drive element movable by said first armature and extending from said casing for connection to the fuel demand adjustment of the fuel control mechanism, and a second drive element movable by the second armature and extending from the casing for connection to the fuel supply adjustment of the fuel control mechanism, the armatures being arranged to be magnetically coupled when the winding is energised so as to transmit movement of the first drive element to the second drive element, but being magnetically uncoupled when the winding is de-energised.

2. A device as claimed in Claim 1, wherein the armatures are slidably received within an elongated non-magnetic guide sleeve around which said winding extends and are movable linearly relative to the sleeve to transmit movement of the first drive element to the second drive element.

3. A device as claimed in Claim 1 or Claim 2, wherein said armatures include respective end surfaces which, when said winding is energised, are magnetically held in abutment to drivingly couple said armatures, de-energisation of the winding serving to release said surfaces so that said first armature is movable relative to the second armature.

4. A device as claimed in Claim 3, wherein said second armature is movable away from the first armature, when the winding is de-energised, to an inoperative position in which said end surfaces are spaced from one another.

5. A device as claimed in Claim 1, and including a fixed stop for defining said inoperative position of the second armature.

6. A device as claimed in Claim 3, wherein resilient means acts on the second armature and is operable, when the winding is de-energised, to urge said second armature against a fixed abutment.

7. A device as claimed in any one of the preceding Claims, wherein one of said first and second armatures is formed with a bore in which at least part of the other armature is slidably received.

8. A device as claimed in any one of the preceding claims, wherein said drive elements are adapted to replace a road vehicle throttle cable.

9. A coupling device for a fuel control mechanism comprising the combination and arrangement of parts substantially as hereinbefore described with reference to and as shown in, Figure 1, or any one of Figures 4 to 6 of the accompanying drawings.

10. A speed limiting system for a road vehicle including a coupling device as claimed in any one of the preceding claims and speed sensitive means operable to deenergise said winding in response to the vehicle road speed reaching a predetermined value.

11. A system as claimed in Claim 10, wherein said speed sensitive means includes a centrifugal switch having a rotatable member adapted to be coupled to a vehicle member which is driven at a speed dependent on the vehicle road speed.

12. A system as claimed in Claim 11, wherein said member is the vehicle speedometer.

13. A speed limiting system comprising the combination and arrangement of parts substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.