United States Patent
`
`[19]
`
`[11] Patent Number:
`
`4,856,850
`
`Aichele et a1.
`
`[45] Date of Patent:
`
`Aug. 15, 1989
`
`[54]
`
`[75]
`
`[73]
`
`[21]
`
`[22]
`
`[63]
`
`[51]
`[52]
`
`[58]
`
`[56]
`
`BRAKING CONTROL SYSTEM FOR A
`TRAILER
`
`Inventors: William H. Aichele; James 0.
`Hopkins, Jr.; Dale H. Krauskopf, all
`of Fort Wayne, Ind.
`
`Assignee: EPCO Products, Inc., New Haven,
`Ind.
`
`3,981,542 9/1976 Abrams et a1.
`......... 303/20
`
`3,993,362 11/1976 Kamins et a1.
`.. 303/21 BE
`
`5/1977 Lang et a1. ............. 303/20
`4,023,864
`
`....... 303/7
`4,033,630 7/ 1977 Hubbard
`
`4,076,327 2/1978 Hubbard ............ 303/20
`4,254,998 3/1981 Marshall et a1.
`..
`..... 303/20
`
`4,295,687 10/1981 Becker et a1. .......... 303/20
`
`8/1983 Frait ................... 303/20
`4,398,252
`.......................... 303/7 X
`4,721,344
`1/ 1987 Frait et a1.
`
`Appl. No.: 205,568
`
`Filed:
`
`Jun. 3, 1988
`
`Related US. Application Data
`Continuation of Ser. No. 920,569, Oct. 17, 1986, aban-
`doned.
`
`Int. Cl.4 ....................... B60T 13/66; F16D 65/36
`US. Cl. ........................................ 303/20; 303/15;
`188/156
`Field of Search ................... 303/6.01, 7, 9.63, 20,
`303/22.l, 22.4; 188/3 A, 156, 158
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`.......................... 323/22
`3,046,470 7/1962 Blocher, Jr.
`
`3,141,530 7/1964 Morley ......
`188/163
`
`3,371,253 2/1968 Hubbard
`317/130
`
`3,423,135
`1/1969 Beltramo
`303/3
`
`3,497,266 2/1970 Umpleby
`303/3
`
`3,503,652 3/1970 Broek ........
`303/3
`
`3,538,392 11/1970 Carmichael
`317/148.5
`3,574,414 4/1971 Jacob ................... 303/7
`
`3,610,699 10/1971 Ladoniczki .......
`303/7
`6/1973 Pokrinchak et a1.
`.
`..... 303/20
`3,738,710
`
`3,780,832 12/1973 Marshall ......... .
`188/3 R
`
`3,856,362 12/1974 Howard
`....... 303/7
`3,861,489
`1/1975 Lang et a1.
`180/103
`
`.
`3,870,981
`3/1975 Patzke et a1.
`.. 188/158
`3,895,683 7/ 1975 Lang et a1. ........... 180/ 103
`
`8/1975 Vangalis et a1.
`..
`.. 303/24 BB
`3,897,979
`3,909,075 9/ 1975 Pittet, Jr. et a1.
`.
`..... 303/24 C
`
`3,953,084 4/1976 Pittet, Jr. et a1.
`.
`..... 303/24 R
`................. 303/24 C
`3,967,863 7/ 1976 Tomecek et a1.
`
`Primary Examiner—Andres Kashnikow
`Assistant Examiner—Timothy Newholm
`Attorney, Agent, or Firm—Jeffers, Hoffman & Niewyk
`
`[57]
`
`ABSTRACT
`
`The trailer brake control system for use in a trailer
`which is adapted to be towed by a towing vehicle. The
`trailer includes an electrically operated braking mecha-
`nism and the towing vehicle includes a brake pedal, at
`least one brake light, and a brake switch operated by the
`brake pedal to energize the brake light. The control
`system includes a short circuit indicator circuit to pro-
`vide a short circuit signal when a short circuit condition
`is detected in the trailer brake mechanism. A manual
`switch is also provided to manually actuate the trailer
`brake mechanism and to provide a manual brake actua-
`tion signal. A second circuit including a NOR gate
`provides a variable amplitude brake actuation signal in
`response to the concurrent closure of the brake switch,
`the absence of a manual brake actuation signal, and the
`absence of a short circuit signal. An indicator light is
`responsive to the brake actuation signal to provide a
`signal indicative of brake actuation. An oscillator cir-
`cuit provides a stream of pulses and a voltage compara-
`tor is responsive to the stream of pulses and to the vari-
`able amplitude brake actuation signal
`to provide a
`stream of variable width drive pulses. The drive pulses
`drive an electronic switch to cyclically and repetitively
`actuate the trailer brake mechanism thereby applying
`braking force to the brakes of the trailer.
`
`8 Claims, 3 Drawing Sheets
`
`BRAKE
`LIGHTS
`
`
`
`BRAKE ACTIVATION
`DETECTION CIRCUIT
`
`26
`
`INDICATOR
`LIGHT
`
`RAMP
`GENERATOR
`
`.
`
` PULSE WIDTH
`
`MODULATED
`
`
`BRAKE DRIVE
`/
`CIRCUIT
`
`- TRAILER
`
`BRAKES
`
`MANUAL
`
`
`
`BRAKE
`SWITCH
`
`
`
`
`SHORT CIRCUIT
`
`AND REVERSE
`
`DETECTOR
`
`
`IO
`
`Curt - Exhibit 1007 - l
`
`Curt - Exhibit 1007 - 1
`
`

`

`US. Patent
`
`Aug. 15, 1989
`
`Sheet 1 of 3
`
`4,856,850
`
`$3.5:
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`Curt — Exhibit 1'007 — 2
`
`Curt - Exhibit 1007 - 2
`
`
`
`
`
`

`

`US. Patent
`
`Aug. 15, 1989
`
`Sheet 2 of3
`
`4,856,850
`
`NO_
`
`Curt — Exhibit 1007 — 3
`
`Curt - Exhibit 1007 - 3
`
`

`

`US. Patent
`
`Aug. 15,1989
`
`Sheet 3 df3
`
`4,856,850
`
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`Curt — Exhibif 1007 — 4
`
`Curt - Exhibit 1007 - 4
`
`

`

`4,856,850
`
`BRAKING CONTROL SYSTEM FOR A TRAILER
`
`This is a continuation of application Ser. No. 920,569,
`filed Oct. 17, 1986, abandoned.
`
`BACKGROUND OF THE INVENTION
`This invention relates to braking systems for trailers
`and, more particularly, to systems for controlling the
`operation of the brakes of a trailer. Trailers, such as
`mobile homes, campers, boat trailers and the like, which
`are towed behind a towing vehicle such as, for instance,
`an automobile, conventionally employ electrical brakes
`which are actuated by electrical interconnection with
`the electrical brake control system of the towing vehi-
`cle. Thus, as the driver of the towing vehicle operates
`the towing vehicle brakes by depressing the brake
`pedal, the electric証 brake system of the trailer is simul-
`taneously operated.
`Control systems for electrically controlling the
`brakes of a trailer are shown in U .S. Pat. No. 3,780,832
`and U.S. Pat. No. 4,254,998, which patents are assigned
`to the assignee of the present invention and which are
`incorporated herein by reference. In general, the sys-
`tems described in the above-identified patents operate
`by electrically interconnecting the pedal-operated
`brake switch with the trailer brake control system. The
`switch operates the towing vehicle brake lights, and,
`therefore, provides an indication that the towing vehi-
`cle brake pedal has been depressed. These prior art
`systems also provide for the gradual application of brak-
`ing force to the trailer brakes so that, when the brake
`pedal of the towing vehicle is depressed, the control
`system automatically and gradu司ly applies power to
`the trailer brakes. However, these prior art control
`systems do not provide an indication to the driver of the
`vehicle of the amount of braking force which is being
`applied to the trailer brakes. It is, therefore, desired to
`provide a control circuit wherein a perceptible indica-
`tion is provided of the braking force which is being
`applied to the trailer brakes.
`Prior art brake control systems have also included
`short circuit protection whereby, despite actuation of
`the towing vehicle brake pedal, no braking force will be
`applied to the trailer brakes when an electrical short
`circuit or overload condition eガsts in the trailer braking
`system and whereby the trailer brake control system is
`disabled to prevent damage to the electrical circuit
`components. However, these prior art control systems
`do not provide an indication to the driver of the towing
`vehicle that such an overload or short circuit condition
`has developed. It is, therefore, desired to provide a
`control system whereby a perceptible, i.e., visible or
`audible, indication is provided to the driver of the tow-
`ing vehicle that a short circuit or overload situation has
`occurred in the electrical circuit of the trailer brake
`control system.
`Another problem with the prior art trailer brake con-
`trol systems has been that the systems and electronic
`circuits therefor have been relatively complicated. The
`electro血c circuits conventionally have used discrete
`circuit components which are arranged in an analog-
`type of electrical circuit. It is desired to provide a sim-
`plified digital type of trailer brake control electrical
`circuit wherein the trailer brakes are actuated by a train
`of pulses whose width is varied in accordance with the
`amount of braking force to be applied to the trailer
`brakes.
`
`2
`Prior art control systems have also provided for ad-
`justrnent of the amount of braking force to be applied to
`the trailer brakes to account for weight variation in
`trailers. However, in some prior art trailer brake control
`systems, such adjustment has been effected by means of
`liquid sensitive switches, such as mercury switches.
`Such switches are also sensitive to the variation in road
`grade so that the braking force applied to the trailer
`brakes would vary as a function of the grade of the road
`being travelled. It is, therefore, desired to provide a
`trailer brake control system which is not affected by the
`up or down grade of a road.
`
`SUMMARY OF THE INVENTION
`
`The present invention overcomes the disadvantages
`of the above-described prior art trailer brake control
`systems by providing an improved trailer brake control
`system therefor,
`The trailer brake control system of the present inven-
`tion, in one form thereof, includes a circuit which is
`responsive to the actuation of the towing vehicle brake
`pedal and in response thereto provides a brake actuation
`signal. The control system further provides an oscillator
`circuit which provides a stream of output pulses. A
`voltage comparator is provided with both the brake
`actuation signal and the stream of pulses to generate a
`stream of modulated pulses whose widths are varied in
`accordance with the amplitude of the trailer brake actu-
`ation signal. The modulated pulses are used to drive an
`electronic switch so that the trailer brakes are cyclically
`energized for periods of time which vary in accordance
`with the widths of the modulated pulses. Thus, the
`average power applied to the trailer brakes is varied in
`accordance with the amplitude of the brake actuated
`signal. The system also includes an indicator to indicate
`to the driver of the towing vehicle the intensity of the
`brake force which is being applied.
`The trailer brake control system in accordance with
`the present invention, in one form thereof, further pro-
`vides a first circuit which is responsive to an overload
`or short circuit condition in the trailer brake electrical
`wiring system and which provides a short circuit signal
`in response thereto. The control system also includes an
`indicator which is responsive to the short circuit signal
`for providing an intermittent perceptible indication
`signal to indicate the short circuit or overload condi-
`tion. In addition, the short circuit signal disables the
`control system from applying power to the trailer
`brakes.
`One advantage of the trailer brake control system
`according to the instant invention is that a perceptible,
`i.e., visible or audible, indication is provided for the
`driver of the towing vehicle to alert him that a short
`circuit or overload condition exists in the wiring of the
`trailer brake control system.
`Another advantage of the trailer brake control sys-
`tern according to the instant invention is that the driver
`of the towing vehicle is warned by means of a flashing
`light that a short circuit or overload condition has de-
`veloped in the electrical circuit of the trailer brake
`system.
`A further advantage of the circuit according to the
`present invention is that a perceptible, i.e., visible or
`audible, indication is provided to the driver of the tow-
`ing vehicle of the amount of braking force which is
`being applied to the trailer brakes.
`
`Curt - Exhibit 1007 - 5
`
`

`

`4,856,850
`
`4
`3
`driver of the towing vehicle of the amount of braking
`Yet another advantage of the present invention is that
`force which is being applied to the trailer brakes.
`the adjustment of the system for trailer weight is not
`Another object of the present invention is to provide
`affected by the up or down grade of the road.
`a trailer brake control system including an indicator
`A still further advantage of the present invention is
`5 device which provides a perceptible visible or audible
`that maximum braking force is maintained on the trailer
`indication to the driver of the towing vehicle that a
`brakes when the towing vehicle and the trailer come to
`short circuit or overload condition has developed in the
`a stop and the towing vehicle brake pedal remains de-
`trailer brake wiring system.
`pressed.
`Still another object of the present invention is to
`A still further advantage of the present invention is
`10 provide a trailer brake control system wherein width
`that the trailer brakes will be automatically disabled
`modulated pulses are generated for actuation of the
`when the towing ve比cle is shifted into reverse gear.
`trailer brakes.
`The present invention, in one form thereof, provides
`A yet further object of the present invention is to
`a trailer brake control system for use in a trailer which
`provide a trailer brake control system wherein the brak-
`is adapted to be towed by a towing vehicle. The trailer
`15 ing power adjustment for trailer weight is not affected
`includes an electric可ly operated brake mechanism and
`by the road grade.
`the towing vehicle includes a brake pedal, at least one
`A still further object of the present invention is to
`brake light, and a brake switch operated by the brake
`provide a trailer brake control system which is disabled
`pedal to energize the brake light. The control system
`when a short circuit or overload condition develops in
`includes a short circuit indicator to provide a short
`20 the trailer brake mechanism.
`circuit signal when a short circuit condition is detected
`A yet still further object of the present invention is to
`in the trailer brake mechanism. A manual switch is
`provide a trailer brake control system wherein the maxi-
`provided for manually actuating the trailer brake mech-
`mum a可u吐ed bra虹ng 釦rce is maintained when the
`anism and for providing a manual brake actuation sig-
`towing vehicle brakes are actuated and the towing vehi-
`nal. A circuit is provided for providing a variable ampli-
`25 cle comes to a stop.
`tude brake actuation signal in response to the concur-
`BRIEF DESCRIPTION OF THE DRAWINGS
`rent closure of the brake switch, absence of a manual
`brake actuation signal, and absence of a short circuit
`The above-mentioned and other features and objects
`signal. An indicator is provided which is responsive to
`of this invention, and the manner of attaining them, will
`the brake actuation signal for providing a perceptible
`30 become more apparent and the invention itself will be
`brake actuation indication signal. An oscillator provides
`better understood by reference to the following descrip-
`a stream of pulses and a voltage comparator is respon-
`tion of an embodiment of the invention taken in con-
`sive to the stream of pulses and the variable amplitude
`junction with the accompanying drawings, wherein:
`brake actuation signal to provide a stream of variable
`FIG. 1 is a block diagram of a preferred embodiment
`width drive pulses. A switch is responsive to the stream
`35 of the invention;
`FIG.ユl and 2b are schematic diagrams of the control
`of variable width drive pulses to cyclically and repeti-
`tively actuate the trailer brake mechanism, thereby
`system of FIG. 1; and
`applying braking force to the brakes of the trailer.
`FIG, 3a and 3b are wave shapes of electrical signals
`The present invention, in one form thereof, provides
`developed in the system of FIG. 1.
`a control system for an electrically operated brake
`40 Corresponding reference characters indicate corre-
`mechanism of the trailer, the trailer being adapted to be
`sponding parts throughout the several views of the
`towed by a towing vehicle. The towing vehicle includes
`drawings.
`a switch responsive to actuation of the brake pedal of
`The exemplifications set out herein illustrate a pre-
`the towing vehicle for providing a brake pedal actua-
`ferred embodiment of the invention, in one form
`tion signal. The control system includes a first circuit
`45 thereof, and such exemplifications are not to be con-
`responsive to the brake pedal actuation signal to pro-
`strued as limiting the scope of the disclosure or the
`vide a trailer brake actuation signal. An oscillator cir-
`scope of the invention in any manner.
`cult provides a stream of output pulses, and a second
`circuit is responsive to both the oscillator circuit and the
`first circuit for cyclically applying power to the brake
`50
`mechanism of the trailer.
`Referring to FIG. 1, there is shown a block diagram
`The present invention, in one form thereof, still fur-
`of a preferred embodiment of the invention. The brake
`ther provides a trailer brake control system for use in a
`lights of the towing vehicle are shown at 12 and are
`trailer which is adapted to be towed by a towing vehi-
`shown connected to a brake activation detection circuit
`cle. The trailer includes an electrically operated brake
`55 14. The brake activation detection circuit 14 also re-
`mechanism. The towing vehicle includes a brake pedal,
`ceives inputs from a manual brake switch 18 and from a
`a brake switch operated by the brake pedal and at least
`short circuit and reverse detector circuit 16. Brake acti-
`one brake light actuated by the brake switch. The con-
`vation detection circuit 14 provides an output to a pulse
`trol system includes a circuit responsive to a short cir-
`width modulated brake drive circuit 20 and to a trailer
`
`cuit condition in the trailer brake mechanism to provide 60 brake indicator light 24. Pulse width modulated brake
`a short circuit signal. An indicator is responsive to the
`drive circuit 20 receives an input from both short circuit
`and reverse detector 16 and ramp generator 22. Pulse
`short circuit signal to provide an intermittent percepti-
`width modulated brake drive circuit 20 provides an
`ble indication signal. A brake actuation circuit is respon-
`output to the trailer brakes 26 and to short circuit and
`sive to operation of the brake switch to operate the
`65 reverse detector 16.
`trailer brake mechanism.
`Referring now to FIGS. 2a and 2b, brake light circuit
`It is an object of the present invention to provide a
`12 is shown at the top left-hand portion of FIG. 2a and
`trailer brake control system including an indicator de-
`comprises brake lights 31 and a single pole, single throw
`vice which provides a perceptible indication to the
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`Curt - Exhibit 1007 - 6
`
`

`

`4,856,850
`
`6
`5
`tive to the grade of the road on which the trailer is being
`brake switch 30 which is actuated by the brake pedal of
`towed.
`the towing vehicle (not shown). Thus, when switch 30
`Comparator 88 also receives an input from a ramp
`is closed, brake lights 31 will be energized from DC
`generator circuit 22 on input lead 90. Ramp generator
`power source B +. The voltage appearing across brake
`5 circuit 22 includes a unijunction transistor 74 of the type
`lights 31 will also be applied to a point intermediate a
`2N6028 which is connected to ground by way of a
`diode 34 and a resistor 36. Resistor 36 forms part of a
`resistor 76. The gate of unijunction transistor 74 is sup-
`resistive divider circuit including resistors 36 and 38.
`plied by means of a voltage divider consisting of resistor
`The junction point between resistors 36 and 38 is con-
`78 and 80. A capacitor 84 is charged by way of resistor
`nected to a NOR nate 32 which is connected as an
`0 82 from the B+ voltage supply. Thus, as the voltage
`inverter. Therefore,- when a positive voltage is applied I
`across capacitor 84 increases in ramp fas瓦on, unijunc-
`to the input of inverter 32, the output will be low. This
`tion transistor 74 will be fired when the voltage across
`output is connected to a NOR gate 44). NOR gates 32
`capacitor 84 reaches the predetermined level set by
`and 40 may be of the type 4025. NOR gate 40 also re-
`resistor 78 and resistor 80. Unijunction transistor 74
`ceives two other inputs. One input is provided from .
`5 will, therefore, discharge capacitor 84 through resistor
`switch contact 48 of manu証 brake switch 18 by way ofl
`76 to ground. Thus, the voltage appearing across capac-
`the resistive divider comprising resistors 42 and 44.
`itor 84 will be a sawtooth wave and this voltage is pres-
`Thus, when manu証 brake switch 18 is closed, power is
`ented by way of resistor 86 to input 90 of comparator
`supplied to contact 48 by way of lead 49 from vehicle
`88. In FIG. 3a, the wave shape appearing at lead 90 is
`hntterv 511 Vehicle battery 50 also orovides nower
`0 shown at 94 and comprises a sawtooth wave. The fre-
`the filtered 2
`through diode 52 to capacitor 51 to provide
`quency of the sawtooth wave may be approximately
`DC supply indicated at B +.
`100 hz. The wave shape appearing on lead 72 has been
`The third input to NOR gate 40 is derived from short
`indicated at 96. For purposes of explanation, wave
`circuit and reverse detector circuit 16 shown in FIG. 2b
`shape 96 is shown as a steady state, DC voltage level. In
`and discussed in detail hereinbelow. 、 For purposes of 2
`5 reality, as explained hereinbefore, voltage 96 will be a
`discussion, assume that all inputs to INUIt gate 'w are
`ramp-shaped voltage which varies much more slowly
`low, thereby indicating that manual brake switch 18 is
`than the frequency of sawtooth wave 94. Once wave
`not actuated, that no short circuit or overload condition
`shape 96 has reached its maximum or DC level, it will
`exists in the trailer brake system 26, and that switch 30
`remain there until the towing vehicle brake pedal is
`is closed because the brake pedal of the towing vehicle1
`0 released.
`has been depressed. The output of NOR gate 40 will,'
`The output of comparator 88 will be high when in-
`therefore, go high, thereby reverse biasing diode 53 and
`puts appear on both leads 72 and 90. Therefore, no
`preventing further flow of current from the B + supply
`output appears once sawtooth wave 94 exceeds voltage
`through resistor 54, potentiometer 56 and diode 53. This
`96. Therefore, as shown in FIG. 3b, an output 100 is
`enables capacitor 58 to charge up at a rate determined3
`5 provided at the output of comparator 88 which corn-
`by the values of resistor 54, potentiometer 56 and capac-
`prises a square wave of the same frequency as the saw-
`itor 58. The rate at which capacitor 58 charges may be
`tooth wave 94 generated by ramp generator 22. It can
`varied by adjusting potentiometer 56. The rate at which
`also be seen that as the voltage 96 increases to 96',
`capacitor 58 charges effects the rate at which power is
`shown in dotted lines because of an adjustment in trailer
`applied to the trailer brakes after the towing vehicle 40
`weight compensation potentiometer 64, the width of the
`brake pedal is depressed. Thus, if maximum resistance is
`pulses of wave shape 100 will increase to 100', shown in
`presented by potentiometer 56, the rate at which brak-
`dotted lines. Therefore, the width of the pulses 100 is a
`ing power will be applied to the trailer brakes will be
`function of the braking power which is to be supplied to
`quite gradual as compared to when minimum resistance
`the trailer brakes. Furthermore, as potentiometer 56 is
`is presented by potentiometer 56.
`4
`5 adjusted, the rate at which voltage 96 reaches its maxi-
`The voltage on capacitor 58 is presented to one of the
`mum value will also vary. Pulse wave 100 is applied by
`inputs of an operational amplifier 60 which is connected
`way of resistor 102 to the base of NPN transistor 104
`as a voltage follower. Therefore, the voltage at the
`and drives transistor 104 into its saturated state. The
`output of operational amplifier 60 will follow the ramp
`collector of transistor 104 is connected by way of a
`voltage appearing across capacitor 58. This voltage is 5
`0 resistor 106 to the positive side of the vehicle battery 50.
`applied through a voltage divider including resistor 62
`The collector is also connected by way of a resistor 108
`and potentiometer 64 via blocking diode 68 to a capaci-
`to the base of PNP transistor 110. Thus, as transistor 104
`tor 66 which is charged thereby. Potentiometer 64 is
`is saturated, the voltage across transistor 104 will be
`used to compensate for the weight of the trailer. Thus,
`very low and will cause transistor 110 to be saturated so
`if a relatively heavy trailer is used, the braking force55
`that transistor 110 presents a very low voltage drop.
`which is applied should be relatively high. Therefore,
`Battery 50, therefore, applies a voltage by way of a
`potentiometer 64 is adjusted for maximum resistance
`resistor 112 to the trailer brakes which are shown at 114.
`whereby maximum voltage appears on capacitor 66. If a
`Thus, transistors 104 and 110 will be alternately
`lightweight trailer is used, less braking force is needed,
`driven conductive and non-conductive by wave shape
`100 so that pulsed power is applied to trailer brakes 114.
`and, therefore, potentiometer 64 is adjusted for less 60
`The average amount of power applied to brakes 114
`resistance, thus causing a lower voltage to appear on
`will, therefore, depend on the width of the pulses. Thus,
`capacitor 66. The voltage appearing across capacitor 66
`when control 64 is set for a heavily loaded trailer, the
`is applied by a resistor 70 to an input 72 of a comparator
`pulse width of pulses 100 will be grdater and, therefore,
`88.
`the average amount of power applied to the trailer
`Since the weight control potentiometer 64 for adjust- 65
`brakes will be relatively great. On the other hand, if
`ing the brake circuit for varying weights of the trailer is
`control 64 is adjusted for a lightweight trailer, pulses
`not dependent upon mercury switches or other liquid-
`100 will be relatively narrow and a relatively low aver-
`type switches, the instant brake control is also not sensi-
`
`Curt - Exhibit 1007 - 7
`
`

`

`4,856,850
`
`8
`7
`Thus, when a high voltage appears at the output of
`age amount of power will be applied to the vehicle
`comparator 148, indicating that a short circuit condition
`brakes. The coils 114 of the trailer brakes integrate the
`e誠sts, diode 174 is forward driven thus causing LED
`applied power pulses because of the coil inductance.
`168 to emit light. The output of comparator 148 is also
`However, because of the relatively steep sides of pulses
`provided to a NOR gate 152. Thus, the output of NOR
`100, negative power spikes will also be generated across 5
`gate 152, due to the high input from comparator 148,
`coils 114. The negative spikes will be clipped off by
`will be low. The output NOR gate 152 is connected by
`diode 116, thereby, eliminating the fly back effect of
`way of a diode 153 to input 72 of comparator 88. When
`brake coils 114. The current conducted by resistor 112
`the output of NOR gate 152 goes low, diode 153 will be
`provides an indication of the amount of power supplied
`
`10 forward biased and will cause input 72 of comparator 88
`to the trailer brakes.
`to go low. Thus, comparator 88 is prevented from pro-
`Turning now to FIG. 2b, it is shown that resistor 112
`viding drive on output 98 to power transistors 104 and
`is connected in parallel with resistor 120. The voltage
`110 to drive brake coils 114. Current sensing resistor
`across current sensing resistors 112 and 120 is applied,
`112, therefore, senses that no current is applied to brake
`by way of blocking diodes 122 and 124 and resistors 126
`coils 114. Thus, comparator 148 will receive no input
`and 130, to the inputs of differential amplifier 132. Resis- 15
`from differential amplifier 132, and the output of differ-
`tor 128 is part of the resistive divider circuit for one of
`ential amplifier 148 will go low. This in turn will take
`the inputs of differential amplifier 132. Resistor 134 and
`away the drive of LED driving transistor 170 to diode
`capacitor 136 provide filtering for the other input of
`174, and LED 168 will, therefore, turn off and no light
`differential amplifier 132. The output of differential
`will be emitted thereby. At the same time, the low sig-
`amplifier 132 is applied, by way of a diode 138, to a 20
`nal provided to NOR gate 40 will enable NOR gate 40
`filtering circuit comprising a resistor 140 and a capaci-
`to provide a high input on its output and will enable
`tor 142. The filtered voltage across capacitor 142 is an
`capacitor 58 to charge up again. Furthermore, NOR
`indication of the average power applied to the trailer
`gate 152 will no longer forward bias diode 153 and will
`brake coils 114. If an overload situation occurs in the
`enable an output to be generated on output 98 of corn-
`trailer brake circuit or if a short occurs in the trailer 25
`parator 88. Power will, therefore, again be provided to
`brake wiring, the amount of current conducted by resis-
`brake coils 114. This in turn will cause an excessive
`tor 112 to trailer brake coils 114 will be very high.
`amount of current which will be sensed by comparator
`Therefore, a high voltage will be presented across resis-
`148, therefore, again presenting a high output value on
`tors 112 and a high voltage will appear across capacitor
`the output of comparator 148, which in turn will again
`30
`142.
`turn off NOR gate 40 and will turn on LED 168, and
`The voltage across capacitor 142 is presented to an
`will turn off comparator 88. Thus, in case of a short
`input of a comparator 148. Comparators 88 and 148,
`circuit or overload condition in the trailer brake circuit,
`differential amplifiers 132 and voltage follower 60 are
`LED 168 will be alternately driven on and off and will,
`all integrated circuits of the type LM2902. The other
`therefore, flash to alert the driver of the vehicle that a
`input for comparator 148 is derived from a resistive 35
`short circuit condition exists. In the disclosed embodi-
`divider including resistors 144 and 146. Resistor 150 is
`ment, the light will flash at a rate of approximately thz.
`part of the biasing circuit for comparator 148. Thus, if
`The flashing of LED 168 alerts the driver of the towing
`the amount of current sensed by resistor 112 exceeds a
`vehicle that a short circuit or overload condition exists
`predetermined level determined by the values of resis-
`in the trailer brake system.
`tors 144 and 146, the output of comparator 148 will be 40
`It should also be noted that the LED flashing light
`high. This high output is presented by way of terminal
`which provides a perceptible indication of both the
`B to the input of NOR gate 40 and will thereby prevent
`amount of braking power which is being applied and of
`NOR gate 40 from providing a brake actuation signal,
`the existence of a short or overload condition in the
`thereby preventing transistor 110 from providing
`wiring, may be replaced with a device which emits an
`45
`power to trailer brake coils 114.
`audible signal wherein the intensity of the sound de-
`Continuing now with FIG, 2a, the output of voltage
`pends upon the amount of brake power applied and
`follower 60 is connected by way of a diode 172 and a
`wherein the audible signal will be turned on and off
`resistor 173 to the base of an NPN transistor 170. Tran-
`cyclically upon the occurrence of a short circuit condi-
`sistor 170 has its collector connected to the B + supply
`tion as described above.
`and drives a light emitting diode (LED) 168 by way of 50
`Another input is provided for NOR gate 152 by the
`a diode 166 and a resistor 164. Diode 168 may be of the
`switch 158 which energizes the backup lights 156 of the
`type 550-2406, manufactured by Dialight. Thus, when a
`towing ve血cle. Thus, when power is applied to the
`voltage appears at the output of voltage follower 60,
`backup lights 156 as the vehicle is shifted into reverse,
`LED 168 will be driven, thereby emitting an amount of
`switch 158 will close and a high voltage will appear at
`light depending upon the amount of voltage present at 55
`the input to NOR gate 152 by way of the resistive di-
`the output of voltage follower 60. Thus, as the brake
`vider network consisting of resistors 154 and 160. B +
`pedal (not shown) of the towing vehicle is depressed
`voltage is also applied by way of switch 158 through a
`and switch 30 closes, the voltage rises in ramp fashion
`diode 162 to a junction point between diode 166 and 164
`on capacitor 58 and the light emitted by LED 168 will
`in the LED circuit. Thus, by reverse biasing diode 166,
`provide a visible indication of the amount of braking 60
`transistor 170 can no longer drive LED 168 and the
`power which is being applied to the vehicle brake coils
`light will turn off when the towing vehicle is shifted
`114. Furthermore, when a short circuit or overload
`into reverse. At the same time, the high input to NOR
`condition is sensed by the short circuit detecto