System for detecting the parking state of a gearbox

Abstract

Transmission diagnostic system, which includes the following: a pivotable element having an element width and pivoting between a locked position and a unlocked position, the locked position corresponding to a PARKING gear step; an actuator (30, 30') having a groove (60) wherein the groove (60) has a first side, a second side and a groove width, wherein the groove width is greater than the element width, wherein the groove (60) holds the pivotable element, wherein the actuator (30, 30') is designed to pivot the pivotable element selectively between the latched position and the unlatched position; a preload spring designed to preload the pivotable element against the first side of the groove (60); and a control (22) designed to generate at least one diagnostic signal in response to the fact that the pivoting element is not in contact with the first side of the groove (60).

Description

TECHNICAL AREA

[0001] The disclosure concerns automatic transmissions and, in particular, wire-shift transmissions. BACKGROUND

[0002] A traditional automatic transmission includes a transmission control device to manage the transmission of a motor vehicle. The transmission control device is used to select several ranges, such as Park, where the transmission is locked to prevent the vehicle from moving; Neutral, where the transmission allows the vehicle to move freely, as when being towed; Reverse, where the transmission allows the vehicle to move backward; and one or more Drive ranges that allow the vehicle to move forward. The transmission control device is usually in the form of a lever connected to the transmission by a mechanical linkage, such as a cable. Typically, the lever is also connected to an indicator.When the transmission control mechanism is moved from one range to another, the mechanical linkage physically shifts the transmission into the selected setting, and the indicator moves to show the driver which range has been selected. Even when the vehicle is switched off, the driver can determine the current transmission range using the indicator and, in some cases, can even put the transmission control mechanism into neutral, for example, if the vehicle is to be towed.

[0003] The traditional automatic transmission uses several friction elements to automatically shift gears. In the broadest sense, these friction elements can be described as torque-receiving elements, although they are more commonly referred to as clutches or brakes. The friction elements establish power transmission paths from an internal combustion engine to a set of vehicle drive wheels. As the vehicle accelerates, the overall gear ratio, which is the ratio of a transmission input shaft speed to a transmission output shaft speed, decreases during an upshift as the vehicle speed increases for a given engine throttle position. A downshift to achieve a higher gear ratio occurs when an engine throttle position increases for any given vehicle speed, or when the vehicle speed decreases as the engine throttle position decreases.A wide variety of planetary gear configurations are found in modern automatic transmissions. However, the basic principle of the shift kinematics remains similar. Shifting an automatic transmission with multiple planetary gear sets is accompanied by the engagement and / or disengagement of friction elements to change speed and torque relationships by altering the torque path through the planetary gear sets. Friction elements are usually actuated either hydraulically or mechanically, depending on the position of the transmission control unit.

[0004] In a shift-by-wire transmission arrangement, the mechanical connection between the transmission control device and the transmission is eliminated. Instead, the transmission control device transmits an electrical signal to an electronic control unit, which instructs separate actuators to engage or disengage the various friction elements to obtain a desired gear ratio. The control device is no longer necessarily in the form of a lever, since it no longer moves a mechanical linkage to control the transmission. Instead, the control device is typically an electromechanical interface (e.g., a series of buttons, a lever, or a toggle) used to instruct the transmission to shift between gear ranges. DE 10 2005 046 610 A1 discloses a parking lock for an automatic transmission in motor vehicles.DE 10 2011 056 725 A1 discloses a device for actuating a parking lock of a vehicle transmission. BRIEF DESCRIPTION OF THE INVENTION

[0005] The object of the invention is to provide an improved transmission diagnostic system, an improved vehicle, and an improved transmission assembly. A transmission diagnostic system according to the present disclosure includes a pivotable element that is pivotable between an engaged and an disengaged position. The engaged position corresponds to a PARK gear position, and the disengaged position corresponds to a gear position other than PARK. The transmission diagnostic system further includes an actuator with a groove. The groove has a first side and a second side, with an opening between the two sides. The width of the opening is greater than the width of the pivotable element. The pivotable element is held in the groove, and the actuator is designed to selectively pivot the pivotable element between the engaged and disengaged positions.The transmission diagnostic system also includes a preload spring designed to apply a preload torque to the pivoting element, thus preloading it against the first side of the groove. The transmission diagnostic system further includes a control unit designed to generate at least one diagnostic signal in response to the pivoting element not being in contact with the first side of the groove.

[0006] In some embodiments, the at least one diagnostic signal includes a first diagnostic signal in response to the pivoting element being in the disengaged position and not in contact with the first side of the groove. The at least one diagnostic signal may include a second diagnostic signal in response to the pivoting element being in the engaged position and not in contact with the first side of the groove. In some embodiments, the transmission diagnostic system additionally includes an angular position sensor, wherein the pivoting element has a pivot axis, and the angular position sensor communicates with the controller and is configured to detect an angular position of the pivoting element.

[0007] A vehicle according to the present disclosure includes a transmission with a switchable element. The switchable element can be selectively engaged with a parking gear to bring the vehicle into the PARK position. The switchable element is movable between a nominal disengaged position, a bypass disengaged position, a nominal engaged position, and a diagnostic engaged position. The transmission further includes an actuator that is driven and coupled to the switchable element. The vehicle further includes at least one control unit. The control unit is designed to generate a first diagnostic signal in response to the switchable element being in the bypass disengaged position and to generate a second diagnostic signal in response to the switchable element being in the diagnostic engaged position.

[0008] In some embodiments, the actuator includes a driven shaft that is movable along a drive axis between a latched position and a disengaged position. The driven shaft has a groove along the drive axis that retains the switchable element, and the switchable element has a bias position and a counter-bias position relative to the groove. The switchable element is biased against the bias position.In such embodiments, the nominal disengaged position corresponds to the driven shaft being in the disengaged position and the switchable element being in the preload position; the nominal engaged position corresponds to the driven shaft being in the engaged position and the switchable element being in the preload position; the bridging disengaged position corresponds to the driven shaft being in the disengaged position and the switchable element being in the counter-preload position; and the diagnostic engaged position corresponds to the driven shaft being in the engaged position and the switchable element being in the counter-preload position.

[0009] In some embodiments, the control unit is further configured to control the vehicle according to a restricted operating strategy in response to the first diagnostic signal. The control unit may also be configured to apply a vehicle parking brake in response to the vehicle being switched to a PARK position and either the first or the second diagnostic signal. Some embodiments additionally include a vehicle information display. In such embodiments, the control unit is further configured to signal a warning to the driver via the information display in response to either the first or the second diagnostic signal.

[0010] A gear assembly according to the present disclosure includes a switchable element designed to selectively engage or disengage from a PARKEN gear. The gear assembly further includes an actuator driven by the switchable element, which holds the switchable element in a preload position or a counter-preload position, and a spring designed to bias the switchable element against the preload position. The assembly further includes a control unit designed to generate at least one diagnostic signal in response to the switchable element being in the counter-preload position.

[0011] Some embodiments additionally include an angular position sensor. In such embodiments, the switchable element has a first end and a second end, wherein the first end is restrained by the actuator, and the second end is pivotable about a pivot axis. The angular position sensor communicates with the controller and is configured to detect an angular position of the switchable element. In such embodiments, the actuator may include a driven shaft that is movable along a drive axis, the driven shaft defining a groove oriented along the drive axis. The groove has a first side, a second side, and a groove width. The first end of the switchable element has a smaller width than the groove width and is restrained by the groove.In the bias position, the switchable element contacts the first side, and in the reverse bias position, the switchable element contacts the second side. In some embodiments, the actuator has an engaged position, corresponding to the switchable element engaging the PARKEN gear, and an unengaged position, corresponding to the switchable element disengaging the PARKEN gear. In such embodiments, the at least one diagnostic signal comprises a first diagnostic signal in response to the switchable element being in the reverse bias position and the actuator being in the unengaged position, and a second diagnostic signal in response to the switchable element being in the reverse bias position and the actuator being in the engaged position.

[0012] Embodiments according to the present disclosure offer a number of advantages. For example, the present disclosure provides a diagnostic system for a transmission that provides diagnostic signals indicating whether the transmission is in a lock-up position or in a diagnostic state. The present disclosure further provides a system for controlling a vehicle in response to the diagnostic signals.

[0013] The above advantages and other advantages and features of the present disclosure will become apparent from the following detailed description of the preferred embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic representation of a vehicle that incorporates a wire-shift transmission; Fig. Figure 2 is an isometric view of a parking assembly of a shift-by-wire transmission that includes a lock-up system; Fig. Figure 3 is an isometric view of a parking bridging system; and Fig. Figure 4 illustrates the operation of a parking override system and sensor. DETAILED DESCRIPTION

[0014] As required, detailed embodiments of the present invention are disclosed herein; however, it is understood that the disclosed embodiments are purely exemplary of the invention, which can be implemented in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of certain components. The specific structural and functional details disclosed herein should therefore not be interpreted as limiting, but merely as a representative basis for teaching a person skilled in the art how the present invention can be carried out in various ways.

[0015] A wire-shift transmission refers to an arrangement that has no mechanical connection between a transmission control device and the transmission. Instead, a user-operated shift module transmits an electrical signal to an electronic control unit, which instructs separate actuators to engage or disengage various friction elements, such as clutches or brakes, to obtain a desired gear ratio. In some embodiments, the transmission may be equipped with a parking pawl actuated by one of the actuators. The parking pawl may engage with at least one gear in the transmission to prevent vehicle movement, or disengage from the at least one gear to allow vehicle movement. The parking pawl may be engaged in response to a driver shifting the transmission into PARK.Of course, other parking elements can also be used to impede vehicle movement, such as a parking brake.

[0016] In some configurations, the actuators that operate the friction elements and the parking pawl may be hydraulic actuators. During normal vehicle operation, an engine drives a transmission pump to provide hydraulic pressure to the actuators, allowing the friction elements to engage or disengage. Because there is no mechanical connection between the shift module and the transmission, a driver will be unable to shift gears if there is no hydraulic pressure at the actuators. When the engine is off, the shift module cannot be used to shift gears.

[0017] Under certain circumstances, it may be desirable to shift the vehicle from PARK to another gear without the engine running. For example, if the engine is inoperable, it may be useful to shift the transmission out of PARK to facilitate towing. Another example is the ability to roll the vehicle to a new location without the engine running. With the standard gearshift module, shifting out of PARK without the engine running is not possible. Therefore, the transmission may be equipped with a manual override mechanism. This could be a mechanism located under the hood or a cable mechanism accessible from inside the passenger compartment.Such solutions can be difficult for a user to access, difficult to install within a vehicle, and can also add complexity and cost to the vehicle. Additionally, known override mechanisms accessible under the hood involve an external override lever that moves during normal transmission operation. Such external moving parts are also susceptible to mud, snow, ice, or other debris accumulating and obstructing transmission operation.

[0018] In Fig. Figure 1 is a schematic representation of a vehicle 10. The vehicle 10 includes a wire-shift transmission 12. The transmission 12 includes an associated parking gear 14, which can be selectively engaged to place the vehicle in the PARK state. The parking gear 14 may include a parking pawl, which can be selectively engaged with an associated gear in the transmission to restrict vehicle movement. The transmission 12 also includes at least one associated actuator 16. The actuator 16 is designed to selectively engage or disengage the parking gear 14 via a switchable element 18. This configuration will be discussed in more detail below.Additional actuators (not shown) can control various other friction devices, such as clutches and brakes, to selectively transfer power from a vehicle engine (not illustrated) to the vehicle wheels (not illustrated) according to different gear ratios.

[0019] The vehicle 10 additionally includes a sensor 20 designed to detect the position of the switchable element 18. The sensor 20 communicates with or is under the control of at least one controller 22. In various embodiments, the controller(s) 22 can be a vehicle system controller or several controllers communicating with each other. The controller 22 also communicates with the transmission 12 or is otherwise designed to control the transmission 12. The controller(s) 22 can, of course, communicate with various other sensors and in the Fig. The vehicle components not illustrated are listed below. The control unit 22 is designed to transmit various messages and / or warnings to a driver display 24. The driver display may include an instrument panel warning light, a multifunction display, a warning tone, or various other methods of communicating information to a user. The vehicle also includes a parking brake 25, which communicates with or is under the control of the control unit 22. The parking brake 25 is preferably an electric parking brake.

[0020] Fig. Figure 2 illustrates an isometric view of a parking assembly of a wire-shift transmission that includes a bypass system. The transmission includes at least one gear set 26. A parking pawl 28 can be selectively engaged with a gear of the gear set 26. When engaged, the parking pawl 28 restricts vehicle movement. An actuator 30, which can be hydraulic or electric, engages or disengages the parking pawl 28 via a connecting arm 32 and a link 34. A parking bypass device 36 operably connects the actuator 30 to the connecting arm 32.

[0021] Fig. Figure 3 illustrates an isometric view of a parking override assembly. An actuator 30', which in this embodiment includes a hydraulic valve, is driven by an inner lever 40. The inner lever 40 is a switchable element driven at its opposite end by a connecting arm 32'. The actuator 30' is movable between different positions, including a first position, which can be a PARKING position in which a parking pawl is engaged on a gear of a transmission, and a second position, which can be a NO-PARK position in which a parking pawl is disengaged from a gear of a transmission. The inner lever 40 is designed to pivot about a pivot axis 42 in response to the actuator 30' moving between the different positions.A torsion spring 44 is designed to exert a preload torque on the inner lever 40. The torsion spring 44 is designed to exert a preload torque on the PARKING position, as will be discussed further below. Such an assembly can be described as having a "return-to-PARKING" function. The inner lever additionally includes a pin 46 extending from a surface opposite the torsion spring 44. It should be noted that "inner" in this context refers to the positioning of the lever relative to a gearbox housing. The inner lever 40 and associated components, including the actuator 30' and the connecting arm 32', are preferably located within the gearbox housing.

[0022] The parking override assembly additionally includes an override lever 50, which is also designed to pivot around the pivot axis 42. The override lever 50 is designed to pivot between different positions, including a first position, which can be a "nominal" position for normal operation, and a second position, which can be an "override" position. The override lever 50 is positioned outside the housing for easier access. The override lever 50 is designed to pivot independently of the inner lever 40, so that the override lever remains stationary when the inner lever 40 pivots between the PARKING and NON-PARK positions during normal operation. The override lever 50 is coupled to an actuator arm or finger 52, so that the override lever 50 and the actuator arm 52 pivot together around the pivot axis 42.The actuator arm 52 is preferably contained within a gearbox housing. The actuator arm 52 defines a plane of pivoting motion that passes through the pin 46 of the inner lever 40. The bypass lever 50 includes a first mounting hole 54 with an associated fastener that secures the bypass lever 50 to the gearbox housing. The bypass lever 50 includes a second mounting hole 55. The bypass lever 50 may also include a tension spring 56 that is coupled to the actuator arm 52 and biases the bypass lever 50 against its nominal position.

[0023] Fig. Figure 4 now shows the interaction of the actuator 30' and the inner lever 40 in detail. In this view, it can be seen that the actuator 30' includes a driven shaft 58. As discussed above, the actuator 30', and more precisely the driven shaft 58, is movable between a PARKING position and a NON-PARK position. The driven shaft defines a groove 60. The inner lever 40 is held within the groove 60.

[0024] As can be seen, the groove 60 defines an inner width that exceeds the outer width of the inner lever 40. The torsion spring 44 (not shown in this view) exerts a preload torque τ on the inner lever 40. For a given position of the driven shaft 58 during nominal operation, the inner lever 40 is held in a preloaded position in which a first side of the inner lever 40 contacts a first side of the groove 60. At the point of contact between the first side of the inner lever 40 and the first side of the groove 60, the inner lever 40 exerts a return-to-park force on the driven shaft 58. When the vehicle is engaged and supplying hydraulic pressure to the actuator 30', the actuator 30' can overcome the return-to-park force to disengage the vehicle from PARK. The preload torque τ acts to return the actuator 30' to the PARKING position in the absence of hydraulic pressure.

[0025] Under certain conditions, the inner lever 40 can move into a counter-preload position in which a second side of the inner lever 40 contacts a second side of the groove 60. This can occur, for example, in the absence of torque from the torsion spring 44 or when a torque on the bridging lever 50 exceeds the preload torque τ.

[0026] The preload and counter-preload positions are separated by an angular gap α. In an exemplary embodiment, α is approximately four degrees. The inner lever 40 has a total angular span β. In an exemplary embodiment, β is approximately 18 degrees.

[0027] An angular position sensor 20' is designed to detect the angular position of the inner lever 40 relative to its pivot axis. The angular position sensor 20' is associated with a controller and is designed to transmit the angular position of the inner lever 40 to the controller. In a preferred embodiment, the angular position sensor 20' comprises a dual-channel sensor with a measuring range that exceeds the expected span β.

[0028] Due to the selective movement of the driven shaft 58 between the PARKING and NON-PARK positions, and due to the fact that the inner lever 40 has both a preload position and a counter-preload position relative to the groove 60, the inner lever 40 consequently has at least four independent modes or positions.

[0029] In the first position, the driven shaft 58 is in the PARKING position and the inner lever 40 is in the preload position. This is a nominal PARKING or nominally engaged position, in which the parking gear is engaged and the inner lever 40 is held back by the torsion spring 44 according to nominal operation.

[0030] In the second position, the driven shaft 58 is in the non-parking position and the inner lever 40 is in the preload position. This is a nominal non-parking or nominal disengaged position, in which the parking gear is disengaged and the inner lever 40 is held back by the torsion spring 44 according to nominal operation.

[0031] In the third position, the driven shaft 58 is in the PARK position and the inner lever 40 is in the counter-preload position. This can occur, for example, if the driven shaft 58, in the absence of preload torque, has moved from the torsion spring 44 into the NON-PARK position and back into the PARK position. This is a diagnostic PARK or diagnostic latched position in which the parking gear is engaged, but the inner lever 40 is not held in its nominal position. In a preferred embodiment, the associated control is configured to signal an initial diagnostic warning in response to the sensor 20' detecting that the inner lever 40 is in the diagnostic latched position. The initial diagnostic warning can be displayed on the driver indicator 24.

[0032] In the fourth position, the driven shaft 58 is in the non-parking position and the inner lever 40 is in the counter-preload position. This can occur, for example, if a user applies a torque to the lock-up lever 50 that exceeds the spring preload torque τ and pushes the lock-up lever 50 into the lock-up position. This is a lock-up or diagnostic disengaged position in which the parking gear is disengaged and the inner lever 40 is not held in its nominal position. In a preferred embodiment, the associated control is designed to signal a second diagnostic warning in response to the sensor 20' detecting that the inner lever 40 is in the diagnostic disengaged position. The second diagnostic warning can be displayed on the driver display 24.

[0033] In some embodiments, the associated control, which, as in Fig. Figure 1 illustrates that a controller 22 can be designed to perform additional functions in addition to signaling the first or second diagnostic warning.

[0034] The control unit 22 can be configured to activate the parking brake 25 in response to the detection that the inner lever 40 is in the diagnostic PARK position, until the initial diagnostic warning has been cleared, when the vehicle is shifted into PARK. Vehicle movement is thus restricted, even if the torsion spring 44 exerts insufficient torque to hold the inner lever 40 in the engaged position.

[0035] The control unit 22 can be configured to activate a Limited Operating Strategy (LOS) mode of the vehicle in response to the detection that the inner lever 40 is in the lock-up position, until the second diagnostic warning has been resolved. In an LOS operating mode, the vehicle can be driven with limited speed and / or power. Since the vehicle would generally only be operated with the inner lever engaged in the lock-up position when the vehicle is in PARK in the event of abnormal behavior of a switchable element, the LOS mode preferably involves blocking any gear ratio that requires the switchable element used in the PARK gear to engage. As in the example above, the control unit 22 can further be configured to activate the parking brake 25 when the vehicle is shifted into PARK.

[0036] Based on the above description, it can be seen that the present disclosure provides a diagnostic system for a transmission that provides diagnostic signals indicating whether the transmission is in a lock-up position or in another diagnostic state. The present disclosure further provides a system for controlling a vehicle in response to the diagnostic signals.

Claims

[1] Transmission diagnostic system, which includes: a pivotable member having a member width and pivotable between a locked position and a unlocked position, the locked position corresponding to a PARK gear position; an actuator (30, 30') having a groove (60), the groove (60) having a first side, a second side and a groove width, the groove width being greater than the element width, the groove (60) holding the pivotable element, the actuator (30, 30') being adapted to selectively pivot the pivotable element between the engaged position and the disengaged position; a bias spring configured to bias the pivotable member against the first side of the groove (60); and a controller (22) configured to generate at least one diagnostic signal in response to the pivotable member not being in contact with the first side of the groove (60). [2] The transmission diagnostic system of claim 1, wherein the at least one diagnostic signal includes a first diagnostic signal in response to the pivotable member being in the disengaged position and not in contact with the first side of the groove (60). [3] The transmission diagnostic system of claim 1, wherein the at least one diagnostic signal includes a second diagnostic signal in response to the pivotable member being in the engaged position and not in contact with the first side of the groove (60). [4] The transmission diagnostic system of claim 1, further comprising an angular position sensor (20'), wherein the pivotable member has a pivot axis (42), and the angular position sensor (20') is in communication with the controller (22) and is configured to detect an angular position of the pivotable member relative to the pivot axis (42). [5] Vehicle comprising: a transmission (12) having a switchable element (18) engageable with a parking gear to place the vehicle (10) in PARK, the switchable element (18) being movable between a nominal disengaged position, a bypass disengaged position, a nominal engaged position, and a diagnostic engaged position, and an actuator (30, 30') being drivably coupled to the switchable element (18); and at least one controller (22) configured to generate a first diagnostic signal in response to the switchable element (18) being in the bypass disengaged position, and to generate a second diagnostic signal in response to the switchable element (18) being in the diagnostic engaged position, wherein the actuator (30, 30') includes a driven shaft (58) movable along a drive axis between an engaged position and an unengaged position, wherein the driven shaft (58) has a groove (60) along the drive axis that retains the switchable element (18), wherein the switchable element (18) has a preload position and a counter-preload position relative to the groove (60) and is preloaded against the preload position, wherein the nominal disengaged position corresponds tothat the driven shaft (58) is in the disengaged position and that the switchable element (18) is in the preload position, the nominal engaged position corresponds to the driven shaft (58) being in the engaged position and that the switchable element (18) is in the preload position, the bridging disengaged position corresponds to the driven shaft (58) being in the disengaged position and that the switchable element (18) is in the counter-preload position, and the diagnostic engaged position corresponds to the driven shaft (58) being in the engaged position and that the switchable element (18) is in the counter-preload position. [6] The vehicle of claim 5, wherein the at least one controller (22) is further configured to control the vehicle (10) according to a restricted operating strategy in response to the first diagnostic signal. [7] The vehicle of claim 5, further comprising a parking brake, wherein the at least one controller (22) is further configured to engage the parking brake in response to shifting the vehicle (10) to a PARK position and to either the first diagnostic signal or the second diagnostic signal. [8] The vehicle of claim 5, further comprising a vehicle information display, wherein the at least one controller (22) is further configured to signal a warning to a driver via the information display in response to the first diagnostic signal or the second diagnostic signal. [9] Gearbox assembly comprising: a switchable element (18) adapted to selectively engage or disengage a PARKING gear; an actuator (30, 30') drivingly coupled to the switchable element (18) and retaining the switchable element (18) in a preload position or a counter-preload position; a spring adapted to bias the switchable element (18) toward the bias position; and a controller (22) configured to generate at least one diagnostic signal in response to the switchable element (18) being in the counter-bias position, wherein the transmission assembly further comprises an angular position sensor (20'), wherein the switchable element (18) has a first end and a second end, wherein the first end is retained by the actuator (30, 30'), and the second end is pivotable about a pivot axis (42), and wherein the angular position sensor (20') is in communication with the controller (22) and configured to detect an angular position of the switchable element (18), wherein the actuator (30, 30') includes a driven shaft (58) movable along a drive axis, wherein the driven shaft (58) defines a groove (60) oriented along the drive axis, wherein the groove (60) has a first side, a second side, and a groove width has,wherein the first end of the switchable element (18) has a smaller width than the groove width and is retained by the groove (60), and wherein the switchable element (18) contacts the first side in the preload position and the switchable element (18) contacts the second side in the counter-preload position. [10] The transmission assembly of claim 9, wherein the actuator (30, 30') has an engaged position corresponding to the switchable element (18) engaging the PARK gear and an unengaged position corresponding to the switchable element (18) disengaging the PARK gear, and wherein at least one diagnostic signal comprises a first diagnostic signal in response to the switchable element (18) being in the counter-bias position and the actuator (30, 30') being in the unengaged position, and a second diagnostic signal in response to the switchable element (18) being in the counter-bias position and the actuator (30, 30') being in the engaged position.

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