United States Patent
`
`[191
`
`[11]
`
`3,909,075
`
`[45] Sept. 30, 1975
`Pittet, Jr. et al.
`
`[54] TOWED VEHICLE ELECTRIC BRAKE
`CONTROL SYSTEM
`
`[75]
`
`Inventors: Rene E. Pittet, Jr., Marshall; Philip
`J. Grant, Homer, both of Mich.
`
`[73] Assignee: Tekonsha Engineering Company,
`Tekonsha, Mich.
`
`[22]
`
`Filed:
`
`Aug. 2, 1973
`
`[21] Appl. No.: 385,102
`
`[52] US. Cl............ 303/24 C; 188/3 R; 188/181 A;
`303/7; 303/20
`Int. Cl} ............................................ B60T 8/14
`Field of Search ................ 188/3 R, 112, 181 A;
`250/215, 231 R, 231 P; 303/3, 7, 15, 20, 21,
`24 R, 24 A, 24 C; 324/162; 340/53, 262
`
`[51]
`[58]
`
`[56]
`
`References Cited
`UNITED STATES PATENTS
`
`2,032,177
`3,497,266
`3,499,689
`3.778.118
`3.779.612
`
`Logan, Jr.......................... 303/24 A
`2/1936
`..... 303/20 X
`2/1970 Umpleby....
`
`3/1970 Carp et a1................ 303/21 P
`
`12/1973
`Podlewski et a1.
`303/21 EB
`Tschannen ..................... 303/21 CG
`12/1973
`
`Primary Examiner—Trygve M. Blix
`Assistant Examiner—Stephen G. Kunin
`Attorney, Agent, or Firm—Beaman & Beaman
`
`[ 5 7 ]
`
`ABSTRACT
`
`An electronic brake control for trailers utilizing sole—
`noid operated electric brakes wherein trailer braking
`is controlled by sensing the rate of deceleration of the
`towing and towed vehicle producing an electric signal
`controlling a voltage controlled oscillator having a
`fixed, frequency output and a variable pulse width, the
`pulse width increasing proportional to the rate of de—
`celeration. The pulse signals are amplified and ener-
`gize the towed vehicle electric brakes in an oscillating
`or pulsed manner to minimize skidding and brake
`locking. A light sensing circuit selectively shielded by
`a pendulum produces the automatic deceleration re-
`sponsive signal, and manual apparatus are employed
`to produce trailer braking without braking of the tow-
`ing vehicle. Additionally, the automatic electric brake
`system control through the brake light circuit is by—
`passed and isolated by actuation of the emergency
`warning brake light system.
`
`6 Claims, 6 Drawing Figures
`
`34-
`
` _0LTAGE
`
`
`
` aREG __
`
`140
`
`Curt - Exhibit 1008 - 1
`
`Curt - Exhibit 1008 - 1
`
`

`

`U.S. Patent
`
`Sept. 30,1975
`
`Sheet 1 of 2
`
`3,909,075
`
`
`
`Curt - Exhibit 1008 - 2
`
`Curt - Exhibit 1008 - 2
`
`

`

`
`
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`Curt - Exhibit 1008 - 3
`
`Curt - Exhibit 1008 - 3
`
`

`

`1
`TOWED VEHICLE ELECTRIC BRAKE CONTROL
`SYSTEM
`
`BACKGROUND OF THE INVENTION
`
`3,909,075
`
`towed vehicle braking systems associated with the
`trailer hitch, the systems of such known pendulum type
`patents also include limitations in operating and manu-
`facturing characteristics rendering the same commer-
`cially impractical.
`
`SUMMARY OF THE INVENTION
`
`The field of the invention relates to electric brake 5
`controls for towed vehicles wherein the rate of vehicle
`deceleration is automatically sensed to produce a
`It is an object of the invention to provide an elec-
`pulsed electric brake actuation of the brakes of the
`tronic towed vehicle brake control system which is
`towed vehicle.
`practical from an operational and economical stand-
`The braking of towed vehicles, such as trailers, is pro- 10
`point, is capable of accurately sensing deceleration of
`duced by several types of systems. In commercial truck
`the towing and towed vehicle, and operates the electric
`vehicles, such as semitrailers, the trailer brakes are nor-
`brakes of the towed vehicle in such a manner as to pro-
`mally pneumatically or vacuum operated, and are di-
`duce optimum brake control, minimizing skidding and
`rectly connected to the braking system of the towing
`brake locking.
`tractor. With smaller towed trailers, particularly those 15
`Another object of the invention is to provide an auto-
`of the type towed by automobiles, such as utility trail-
`matic electric brake control for towed vehicles wherein
`ers, boat trailers, and recreational vehicle trailers, it is
`a pulsed actuation of the towed vehicle electric brakes
`well known to employ electric brakes on the trailer
`is produced during braking, the duration of the pulse
`wheels to improve the stopping characteristics. Such
`being proportional to the rate of deceleration thereby
`automobile-trailer braking systems usually employ 20
`automatically producing a relationship between the de-
`electric solenoid operated brakes with the trailer, and
`gree of braking required, and the rate of deceleration.
`an electric brake controller mounted in the automobile
`Another object of the invention is to provide an elec-
`adjacent the steering column is usually connected to
`tronic brake control system wherein the control circuit
`the automobile hydraulic braking system for automatic
`25
`operation by the automobile braking system, and also
`is automatically energized from the energizing of the
`usually includes a manual control whereby the trailer
`towing vehicle brake light circuit during braking, but
`the system utilizes means preventing actuation of the
`brakes may be actuated separately from the automobile
`brake control circuit when the brake light circuit is en-
`brakes.
`ergized by the towing vehicle emergency warning light
`Electric trailer brake controllers operated by auto-
`30
`system connected to the brake lights.
`mobile hydraulic brake systems are relatively compli-
`cated to install in that connection to the automobile
`In the practice of the invention the towed vehicle uti-
`lizes electric brakes, such as of the solenoid type. De-
`braking system is required. Additionally, as the braking
`celeration sensing means, such as in' the form of a pen-
`characteristics of an automobile hydraulic system vary
`as the automobile brake shoes wear, known available
`dulum, is mounted upon the towing vehicle and
`35
`towed vehicle braking systems of the aforementioned
`through electrical means, such as a light interruption
`type have not proven completely reliable in operation
`circuit, produces an electronic signal proportional to
`the rate of towing vehicle deceleration. This signal is
`and leave much to be desired with respect to sensitivity
`used to control a voltage controlled oscillator having a
`of operation, optimum braking application, and safety.
`This type of system is difficult to adjust so that the
`constant frequency output, and the oscillator output
`40
`proper amount of trailer braking is produced under all
`signal as determined by the pendulum has a pulse width
`conditions of automobile braking, and under adverse
`which increases proportionally to the rate of decelera-
`road conditions where the road surface is wet or slip-
`tion. The output of the voltage controlled oscillator is
`pery braking situations may arise where known trailer
`amplified and energizes the solenoids of the towed ye-
`hidle electric brakes in the manner determined by the
`brake systems actually produce unsafe braking charac-
`45
`teristics and may cause the trailer to "jacknife."
`pulsed output of the voltage controlled oscillator. The
`Various towed vehicle braking systems have been
`degree of braking of the towed vehicle is thereby pro-
`proposed wherein the braking of the trailer is automati-
`portional to the rate of deceleration of the towing vehi-
`cally controlled by the sensing of deceleration forces.
`cle and is automatically achieved without direct con-
`U.S. Pat. Nos. 2,242,153; 2,642,961; 2,779,443;
`nection to the towing vehicle hydraulic brake system.
`50
`The installation of a brake system in accord with the
`2,856,036 and 2,969,857 disclose automatic brake ap-
`plying apparatus wherein the deceleration inertial force
`invention is simplified as compared with towed vehicle
`braking systems connected to the towing vehicle hyー
`imposed upon the hitch by the trailer during decelera-
`draulic brake system as the control housing is merely
`tion of the towing vehicle is sensed and used to produce
`mounted on the towing vehicle near the driver and only
`a braking of the towed vehicle. Such systems as dis-
`55
`closed in these patents have not enjoyed commercial
`electrical connections are required.
`success, and their complexity and limitations of opera-
`The brake system of the invention includes a manual
`tion have rendered the same generally unacceptable
`control wherein the pulsed braking signals can be im-
`posed upon the trailer brakes without actuation of the
`from a practical point of view.
`
`It has also been proposed to use pendulum or mass 6n towing vehicle braking system and stoplights, and in
`movement sensing devices for sensing deceleration of ー
`this manner manual control of the trailer brakes may be
`a towed and towing vehicle wherein the pendulum op-
`achieved under those circumstances wherein such
`erates a braking circuit of the towed vehicle, either me-
`manual control is desirable and trailer braking without
`braking of the towing vehicle is required.
`chanical or electric, in dependence upon the degree of
`the deceleration occurring・U・S・Pat・Nos・2,870,8766く
`The preferred apparatus for sensing deceleration
`and 3,053,348 disclose such pendulum sensing systems.ー
`forces is by means of a weighted pendulum having a
`While such pendulum type systems have the capability
`light impervious shield mounted thereon. The shield is
`of a higher degree of sensitivity than inertia force
`interposed in a light path generated by a light source,
`
`Curt - Exhibit 1008 - 4
`
`'
`

`

`3,909,075
`
`3
`and sensed by a photo cell device which comprises a
`light sensitive resistance permitting increased current
`to pass upon the photo cell receiving an increased
`amount of light. Deceleration forces imposed upon the
`pendulum tend to move the pendulum mounted shield
`from the light path increasing the current through the
`photo cell, and this system permits a high degree of sen-
`sitivity in that no frictional forces exist between the
`pendulum and the pendulum movement sensing appa-
`ratus. The pendulum and light sensing apparatus is
`mounted upon a support pivotal about an axis trans-
`versely disposed to the direction of towed vehicle
`movement, and adjustment means permit the support
`member to be horizontally adjusted about its axis for
`orienting the pendulum to its optimum position with
`respect to the towing vehicle in which it is mounted.
`Such adjustment permits "leveling" of the pendulum
`with respect to the towing vehicle, and assures unifor-
`mity of braking operation, and permits the operator to
`slightly vary the braking conditions in accord with his
`particular wishes.
`
`4
`control 26, connected to the brake light conductor 38,
`will energize the automobile brake lights 14.
`An automobile emergency warning switch 40 is also
`connected to the battery 12 and the brake light con-
`5 ductor 38, and upon closing of the warning switch 40
`the brake lights 14 will simultaneously flash, as is well
`known. The flashing mechanism for the warning system
`is not illustrated, but is of a conventional nature. The
`brake control 26 is grounded to the vehicle by conduc-
`10 tor42.
`As will be appreciated from the following descrip-
`tibn, the brake control 26 senses deceleration of the
`towing vehicle 10 and the towed vehicle 18, producing
`a pulsed amplified signal energizing the trailer brakes
`15 22 for braking the trailer wheels to a degree propor-
`tional to the rate of deceleration produced by the
`driver braking the towing vehicle 10. As will be appre-
`ciated, there is no connection between the brake con-
`trol 26, and the conventional hydraulic brakes of the
`20
`towing vehicle, not shown, and the brake control in ac-
`cord with the invention is self contained and of an elec-
`tronic nature.
`The brake control 26 may be mounted within a hous-
`ing such as illustrated in FIG. 2. The housing 44 in..
`The aforementioned objects and advantages of the
`25
`eludes a base 46, and a cover 48 which may be re-
`invention will be appreciated from the following de-
`moved to provide access to the housing interior. The
`scription and accompanying drawings wherein:
`mounting bracket 50 permits the housing to be at-
`FIG. 1 is a schematic illustration of a towing and
`tached to the towing vehicle where desired, and, usu-
`towed vehicle illustrating the basic braking circuit and
`ally, the brake control housing will be attached to the
`components of the invention, and the emergency warn-
`30
`steering column, as to be within easy reach of and at a
`ing light system,
`convenient angle to the towing vehicle driver.
`FIG. 2 is a perspective view of the housing for a brake
`The housing exterior includes a gain potentiometer
`control in accord with the invention,
`adjustment knob 52, a pendulum support adjustment
`FIG. 3 is an enlarged perspective view of the housing
`knob 54, a manually operated linear potentiometer
`of the brake control with the cover removed, and par-
`35
`slide knob 56 horizontally movable within the housing
`tially broken sections are taken through the pendulum
`slot 58, and a braking indicator light 60 visible to the
`and associated apparatus,
`driver.
`FIG. 4 is an elevational, sectional view taken through
`The base 46 supports a circuit board 62, and a sup-
`the pendulum support along section IV-IV of FIG. 3,
`port bracket 64 for the power transistor 66 and other
`FIG. 5 illustrates the circuit of the brake control in
`40
`electronic components. The electronic components are
`accord with the invention, and
`mounted at the "front" of the housing, i.e. at the for-
`FIG. 6 is a graph illustrating the relationship between
`ward portion of the housing with respect to the direc-
`braking pulse widths and constant frequency.
`tion of travel of the towed vehicle, which is to the right
`as viewed in FIGS. 2 and 3.
`45
`At the rear of the base 46 the pendulum and light
`sensing apparatus is mounted and includes a U-shaped
`bracket 68 having a pair of spaced uprights 70 pivotally
`supporting a shaft 72 extending between the bracket
`uprights. Shaft 72 has a worm wheel 74 affixed thereto,
`50
`and the worm wheel includes teeth meshing with a
`worm 76 fixed upon the worm shaft 78 rotatably
`mounted within the base upon bearing brackets 80.
`The shaft 72 is rotated by the driver exteriorly of the
`housing by the knob 54. A torsion spring 82 mounted
`upon the shaft 72 imposes a biasing force upon the see-
`tor 74 about the shaft axis as one end of the spring is
`attached to a fixed bearing bracket 80. In this manner
`backlash or vibration between the worm wheel sector
`74, and the worm 76 due to gear teeth clearance is
`60
`eliminated as the torsion spring will always maintain
`engagement of the sector gear teeth with one side of
`the teeth of the worm.
`The support member housing 84 for the pendulum
`and light sensing apparatus is attached to the shaft 72,
`65
`and is of a bell or triangular configuration having an in-
`creased dimension at i惚 lower regions. The support 84
`houses the pendulum 86 which is in the form of a thin
`
`In FIG. 1 a schematic illustration of the braking sys-
`tern in accord with the invention is illustrated. The tow-
`ing vehicle 10, usually an automobile or pickup truck
`includes a battery 12, brake lights 14, and a trailer
`hitch at 16. The towed vehicle, such as a travel trailer
`18, is mounted upon road wheels 20, and each wheel
`has an electric solenoid operated brake 22 of conven-
`tional construction utilizing a solenoid coil 24 for actu-
`ation purposes.
`The brake control mechanism is represented at 26,
`and includes an output conductor 28 extending to the
`trailer brake solenoids, which are connected in parallel,
`and a ground conductor 30 extends from the brake cir-
`cuit to the vehicle 10. Of course, the battery 12 is
`grounded to the vehicle 10, and the other pole of the
`battery is connected to the brake control 26 through a
`fused conductor 32, and the stoplight switch 34. The
`stoplight switch 34 is controlled by the hydraulic pres-
`sure within the automobile braking system in the con-
`ventional manner, and upon the automobile brakes
`being applied conductor 36 extending from the brake
`
`55
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`Curt - Exhibit 1008 - 5
`
`

`

`3,909,075
`
`6
`5
`brakes by the potentiometer actuating knob 56 which
`cantilevered spring member affixed at its upper end to
`controls potentiometer 104. The manual switch 110 is
`the shaft 72, and having a lower end including a
`represented as a separate switch but it will be under-
`weighted rivet member 88, and a shield 90 which ex-
`stood that switch 110 may be built into potentiometer
`tends in the direction of movement of the vehicles. The
`5 104 for closing during the initial actuation of the poten-
`material of the pendulum 86 is of a light weight such
`that the pendulum is sensitive to deceleration and ac-
`tiometer.
`The voltage controlled oscillator circuit described
`celeration forces of the towing vehicle, and will readily
`above is connected to the photo cell 94, which corn-
`deflect in a direction parallel to vehicle movement as
`prises a light sensitive resistance permitting more cur-
`the deceleration, or acceleration, forces vary. The pen-
`dulum 86 preferably consists of a lamination of two 1 0 rent to pass therethrough the greater the amount of
`
`light received by the photo cell. The photo cell 94 may
`leaves of a material such as beryllium copper or phos-
`be of the type commercially available as a Clairex
`pher bronze bonded together with a nonbrittle shear
`CD705.
`resistant resin. This construction dampens the move-
`ment of the pendulum when subjected to sudden forces
`The light emitting diode 92 is so related to the photo
`other than deceleration, such as road shocks. The I 5 cell 94 as to direct its light thereon, except when
`
`shielded by the pendulum shield 90, and a thermistor
`shield 90 is formed of metal and is, of course, impervi-
`112 of 10,000 ohm value plus or minus 10% at 25。 C .
`ous to light.
`maintains a constant current through the light emitting
`A light emitting diode 92 is located within the sup-
`diode 92 regardless of temperature or voltage changes
`port member 84, and is fixed to the support, and is
`fixed relative to the pendulum 86. A photo cell 94 is 2 0 and serves as a regulator for the light emitting diode.
`
`10K ohm resistance 114 is also included in this circuit.
`also mounted upon the support member 84 in opposed,
`spaced relationship to the light emitting diode 92, and
`Transistor 116 is controlled by the thermistor 112 and
`is so positioned as to receive light from the diode. The
`is part of the constant current control circuitry for the
`light shield 90 extends between the diode and the photo
`light emitting diode 92, as is 4.7K ohm resistance 118,
`5 and the 470 ohm potentiometer 120 employed to set
`cell, and will normally interrupt the light from the 2
`the current of the light emitting diode at a particular
`diode preventing such light to be received by the photo
`cell. However, under conditions of deceleration the
`voltage. Thus, this circuitry will assure a predetermined
`pendulum 86 will swing to the right, FIG. 3, and light
`light intensity at the light emitting diode 92 to produce
`passing around the free end of the shield 90 from the -
`consistent braking results under various ambient tern-
`0 peratures and conditions.
`diode 92 to the photo cell 94 will vary the resistance of -
`The circuit associated with the photo cell 94 controls
`the photo cell to produce a braking electronic signal.
`the output of the voltage controlled oscillator 100, and
`The support member 84 is substantially light proof,
`the resistances 106 and 108 and potentiometers 102
`and the rotation of the knob 54, and shaft 78, will pro-
`- and 104 are so determined that the output of the volt-
`duce a rotation of the shaft 72 about its axis which is
`
`transverse t~ the directi~n of vehicle travel. Such ad-3 "age controlled oscillator is at a constant frequency, but
`justment of the support member 84 will vary the orien-
`the width or duration of the pulse signal from oscillator
`tation of the pendulum to the vertical, and, of course,
`will vary in accord with the current flow into the oscil-
`lator. The greater the current flow through photo cell
`cause the light shield 90 to vary slightly with respect to
`94. the longer the Dulse of the signal for each cycle of
`the light oath between the light emitting diode 92 and
`the photo cell 94. The adjustment of the support mem- 4
`0 oscillation from the oscillator output conductor 122.
`ber 84 is basically for the purpose of calibrating the
`A 100pf capacitor 124 and an 82K ohm resistance
`brake control to the horizontal. The amount of adjust-
`126, are interposed between ground and the voltage
`controlled oscillator 100 to complete the oscillator cir-
`ment will vary in each installation depending on how
`the hc,iisin ' 44 is mounted, and the amount of weight
`cuit.
`赫。論命n the t～而g vehicle by the towed vehiみe.
`5 The output of the voltage controlled oscillat~r 100 is
`By experience, the operator will soon locate that ad-
`received by a Darlington transistor amplification cir-
`cuit 128 which also includes 5.1K ohm resistor 130,
`justment of the pendulum and support member which
`and 4.7K ohm resistor 132 which connect to the pri-
`produces the braking characteristics he desires, and by
`mary voltage sunnlv conductor 32 th,e to the 司t-ucino of
`the adjustment of the knob 54, it is possible, within rel- く
`、’the stoplight switch 34, under automatic control of the
`atively narrow limi加, to adjust the sensitivity of the -'
`pendulum movement to deceleration forces.
`trailer brake circuit, or due to the closing of the manual
`With reference to FIG. 5, the circuit of the preferred
`switch 110 during manual control of trailer braking.
`embodiment of the invention will be described.
`The Darlington amplifier controls the output of the
`The circuit is supplied from the electrical system of く くPNP 20 amp power transistor 66 whose circuit includes
`
`"the 270 ohm resistor 134 and the 25 ohm, 15 watt resis-
`the towing vehicle 10 represented by battery 12, whichJ
`will normally supply approximately 12 volts DC. This
`tor 136. The power transistor 66 is connected to the
`supply is fused at 96 and connected to a voltage regula-
`brake solenoid coils 24, and the output is also con-
`tor 98 having a constant output of 8 volts at positive po-
`nected to the indicating lamp 60 mounted upon the
`hrっレp パハnt,.ハlh ハIlQIflfl tハ hrハH,1一a り、，;e.，り1 ;.，』；一．-..;...,
`でーででで‘~：』～“り…，~I：か～"~～一l。’」“l "'"”ー“"v'
`tential. This constant voltage source is connected to aA
`0
`control circuit for the voltage controlled oscillator 100
`that braking is occurring. The circuit includes 3 amp
`consisting of an adjustable gain potentiometer 102 of
`diodes 138 which are for the purpose of protecting the
`50K ohms, the manually adjustable linear potentiom-
`transistor 66 from transients or voltage spikes, as does
`eter 104 of 300K ohms, a 33K ohm resistance 106 and
`0.0lmf capacitor 140.
`a 22K ohm resistance 108. The potentiometer 104 is '
`In the disclosed circuit it is to be understood that the
`mechanically connected to manual switcn iu WfllCfl is
`voitage controilea oscillator 1(10, and its control cir-
`closed upon operation of the manual potentiometer
`cuit, including the light emitting diode 92 and photo
`104 when it is desired to manually actuate the trailer
`cell 94, will always be "on" when the vehicle is in oper-
`
`Curt - Exhibit 1008 - 6
`
`

`

`3,909,075
`
`5
`
`8
`7
`the towing vehicle stoplights 14, it is not desired that
`ation. Thus, no warmup period of the components for
`the towed vehicle brakes be applied each time the stop-
`sensing deceleration are required.
`lights are energized. To prevent such occurrence, a
`However, as the amplification circuitry is not ener-
`diode 142 is placed in conductor 36 permitting energi-
`gized until the stoplight switch 34 is closed, or manual
`zation of the stoplights when the stoplight switch 34 is
`switch 110 is closed by potentiometer 104, this portion
`closed, but preventing a feedback of current into the
`of the circuit remains deenergized until immediately
`brake control 26 when the emergency warning switch
`needed.
`40 is closed.
`If the driver slightly decelerates, such as by taking his
`We claim:
`foot from the towing vehicle throttle, but not applying
`1. An electronic brake control system for towed vehi-
`l
`the hydraulic brakes, the pendulum 86 may be dis-
`0 dles having electric brakes comprising, in combination,
`placed slightly, perhaps permitting light to fall upon the
`a pendulum having a mass defined thereon and having
`a path of movement parallel to the direction of towed
`photo cell 94 producing a pulsed signal from the volt-
`vehicle travel, a light source comprising a light emitting
`age controlled oscillator 100. However, as the stoplight
`diode, a light control member comprising a light imper-
`switch 34 has not been closed, and assuming that the
`15 vious shield, a light sensing member comprising a vani-
`manual potentiometer 104 and switch 110 have not
`able resistance photo cell adapted to receive light from
`been actuated, no braking of the trailer brakes will oc-
`said light emitting diode, one of said members being
`cur. Upon the operator applying sufficient pressure to
`mounted on said pendulum and the other member
`the towing vehicle brake pedal to close the stoplight
`being fixed with respect to said pendulum, said light
`ーハsensing member having a variable electrical resistance
`switch 34, primary current will then be supplied to the
`乙Uproportional to the amount of light sensed thereby, a
`amplification circuitry permitting the power transistor
`66 to impose a pulsed energizing signal upon the brake
`voltage controlled oscillator having an input controlled
`solenoid coils 24 thereby applying the trailer brakes in
`by said light sensing member and having an oscillating
`voltage output having oscillation characteristics deter-
`a pulsating manner, the duration of pulsation per cycle
`mined by the current flow through said light sensing
`of frequency of the signal being determined by the cur-
`25 member, and means connecting said oscillating output
`rent being supplied to the voltage controlled oscillator
`to the towed vehicle electric brakes producing a pulsed
`as determined by the amount of light falling on the
`actuation of the towed vehicle electric brakes during
`photo cell 94, under automatic operation, or deter-
`braking proportional to the amount of light sensed by
`mined by the manual control of the potentiometer 104
`said light sensing member.
`through knob 54. Thus, as soon as the switch 34 or the
`スn 2. In an electronic brake control system for towed ye-
`ーhidles as in claim 1 wherein said shield is mounted upon
`switch 110 is closed, current is available for actuating
`the towed vehicle brakes, and no delay in operation will
`said pendulum and said light sensing member and light
`be experienced if a braking signal is indicated at the Os-
`emitting diode are fixed relative to said pendulum.
`cillator output conductor 122. The braking "feel" or
`3. An electronic brake control system for towed vehi-
`characteristics may be adjusted by regulating the gain
`- - dles having electric brakes comprising, in combination,
`"a pendulum having a mass defined thereon and having
`potentiometer 102 by knob 52. As some drivers desire
`a path of movement parallel to the direction of towed
`a more sensitive and responsive automatic braking ac-
`vehicle travel, a light source, a light control member,
`tion than others this adjustability of the circuit will ac-
`a light sensing member, one of said members being
`commodate individual preferences.
`mounted on said pendulum and the other member
`In FIG. 6 a graphic illustration appears indicating the
`40 being fixed with respect to said pendulum, said light
`type of braking signal which may be produced by the
`sensing member having a variable electrical resistance
`circuit of the invention for pulsing the towed vehicle
`proportional to the amount of light sensed thereby, a
`electric brakes. In FIG. 6 the cycle of the voltage con-
`support member having a pivot shaft transversely dis-
`trolled oscillator 100 is represented at the horizontal
`posed to the direction of towed vehicle travel, adjust-
`,,に ment means connected to said support member for piv-
`ordinate, and the braking pulses are represented by the
`
`signal appearing above the zero lines. For instance, a "Jotally adjusting said support member about said shaft
`to vary the orientation of said support member to the
`25% pulse width which would represent small braking
`horizontal said pendulum and said light sensing mem-
`forces, appears at the top of the graph, and a braking
`ber being mounted on said support member wherein
`pulse for actuating the brake solenoids occurs only
`the horizontal orientation and characteristics of move-
`25% of the time of each cycle. Twice as much braking
`50 ment of said pendulum is adjusted by said support
`occurs at a 50% pulse width, and three times the brak-
`member being adjusted relative to said shaft, a voltage
`ing occurs at 75% of the pulse width. It is not antici-
`controlled brake control circuit having an input con-
`pated that the pulse width will be much greater than
`trolled by said light sensing member and having a volt-
`95% of a cycle, which would represent maximum brak-
`age output determined by the current flow through said
`ing, yet a momentary release of the brake solenoid still
`55light sensing member, and means connecting said out-
`exists to safeguard against skids and brake locking.
`put to the towed vehicle electric brakes producing ad-
`It will therefore be appreciated that the pulsed signal
`tuation of the towed vehicle electric brakes during
`produced by the towed vehicle braking circuit of the
`braking proportional to the amount of light sensed by
`said light sensing member.
`invention provides a superior braking action proving
`4. In an electronic brake control system for towed ye-
`improved safety features, particularly on wet or slip-
`60 hidles as in claim 3 wherein said pendulum is mounted
`pery road surfaces.
`upon said pivot shaft.
`With reference to FIG. 1, it is required by present
`5. In an electronic brake control system as in claim
`safety laws that vehicles include an emergency warning
`4, said light control member comprising a light impervi-
`flasher system for simultaneously flashing the brake
`ous shield mounted upon said pendulum.
`lights and front parking lights of vehicles under certain
`65 6. In an electronic brake control system for towed ye-
`conditions, such as stopping on a right of way, or to in-
`hidles as in claim 5 wherein said light source and light
`dicate slow moving vehicles. Of course, when the ener-
`sensing member are fixed relative to said pendulum.
`gizing warning switch 40 is closed causing a flashing of
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`Curt - Exhibit 1008 - 7
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