TRACTOR CAB SUSPENSION SYSTEM

Abstract

TRACTOR CAB SUSPENSION SYSTEM The invention relates to a suspension system for an agricultural tractor cab on a tractor chassis, connecting said cab and said chassis. The suspension system has vertical mechanical linkages comprising at least one non-suspended articulated mechanical linkage at the front of the cab; two suspended mechanical linkages, each comprising a hydraulic cylinder, arranged at the rear of the cab; the system further comprising a hydraulic circuit including, for each cylinder, at least one pressure accumulator, and two lines fluidly connecting, respectively, the piston side of the cylinder of each suspended linkage to the rod side of the cylinder of the other suspended linkage so as to form a hydraulic interlock of the cylinders. Figure for the abstract: Figure 3

Description

Title of the invention: TRACTOR CAB SUSPENSION SYSTEM Technical field of the invention

[0001] The invention relates to a tractor cab suspension system. More particularly, the invention relates to an agricultural tractor cab suspension system comprising a non-suspended articulated mechanical linkage, two suspended mechanical links, and a hydraulic control device for the suspended links. Technological background

[0002] The cab suspension of a tractor is a crucial component in the driver's perceived comfort. In work machines, and particularly in agricultural tractors, the cab's attachment and fixing points relative to the chassis, as well as the suspension and damping components, are essential to providing the driver with the best possible comfort.

[0003] In a more concrete kinematic approach at the user level, it is then necessary to control the movements induced by the suspension system, such as pitch, roll, and yaw movements. Each of these movements corresponds respectively to a rotation around a transverse, longitudinal, and vertical axis.

[0004] Known cab suspension systems generally use springs, shock absorbers, and other motion control devices to absorb road shocks and vibrations, thereby improving driver comfort. In practice, most of these systems reduce the negative effects of driving and can contribute to a better working environment for the operator.

[0005] Existing cab suspension solutions are diverse. From a structural or mechanical connection point of view, the cab is generally connected to the chassis by three or four attachment points, with either suspended or unsuspended connections. Suspended and unsuspended connections are mechanical links between the cab and the chassis, arranged between the cab and the chassis. A suspended connection is defined as one designed to suspend the cab relative to the chassis; this connection may include springs, shock absorbers, and other motion control devices to absorb shocks and vibrations. An unsuspended connection, on the other hand, can be defined as a link between the cab and the chassis that does not include such means.

[0006] In this regard, prior art is known of tractor cabs with four attachment points, two of which include mechanically suspended connections, pneumatic The suspension is either mechanically or hydropneumatically at the rear of the cab. The unsprung mounting points at the front include flexible vibration-damping mounts, commonly known as "silent blocks," or conical mounts. In this configuration, power transmission at the front of the vehicle is not permitted; there is no roll movement, only pitching.

[0007] Four-point suspension systems are also known, where the four points are suspended mechanically, pneumatically, or oleopneumatically. In this configuration, roll control is achieved with anti-roll bars, which complicates the integration between the cab and the chassis and can result in a higher design cost.

[0008] Some four-point configurations also offer oleopneumatic suspended links at the rear, the combination of which with an anti-roll bar or with mechanical means aimed at increasing the stiffness of each suspension element makes it possible to limit the production of rolling movement; however, these configurations do not include integrated anti-roll management.

[0009] In addition, there is also a three-point pneumatically suspended cab suspension system. Anti-roll control is achieved by adding stiffness to the suspension points, which limits roll movement at the expense of pitch movement. Consequently, user comfort during pitching is not optimized.

[0010] There is therefore a need to provide a suspension system for the cab of an agricultural tractor that overcomes the drawbacks of the prior art. Objectives of the invention

[0011] The invention aims to provide a suspension system for a cab of an agricultural tractor to improve user comfort.

[0012] The invention also aims to provide, in at least one embodiment, a suspension system allowing controlled management of roll and pitch movement while prohibiting yaw movement.

[0013] The invention also aims to provide, in at least one embodiment, a suspension system to facilitate the integration of an anti-roll system.

[0014] The invention also aims to provide, in at least one embodiment, a suspension system comprising hydraulic anti-roll management.

[0015] The invention also aims to provide, in at least one embodiment, a suspension system having a moderate cost. Description of the invention

[0016] One object of the present invention is to overcome the drawbacks of the prior art, To this end, the invention relates to a suspension system for a cab of an agricultural tractor on a tractor chassis, said chassis extending in a longitudinal direction corresponding to the direction of travel of the tractor, said cab extending above the chassis, said system comprising vertical mechanical links connecting said cab and said chassis, said suspension system wherein said vertical mechanical links comprise at least:

[0017] - a non-suspended articulated mechanical joint whose articulation is a joint ball joint, said link being arranged longitudinally at the front of the cabin;

[0018] - two suspended mechanical links each comprising a hydraulic cylinder double-acting, said cylinder having a piston side and a rod side, said suspended links being arranged longitudinally at the rear of the cabin and spaced transversely opposite each other;

[0019] and in that it comprises a hydraulic circuit including, for each cylinder, at least one pressure accumulator fluidly connected to said cylinder, and two lines fluidly connecting respectively the piston side of the cylinder of each suspended link to the rod side of the cylinder of the other suspended link so as to form a hydraulic interweaving of the cylinders.

[0020] Throughout the following description, the terms "longitudinal," "transverse," or "vertical" refer to a cab suspension system as arranged in a tractor. Furthermore, the X-axis corresponds to the longitudinal axis of the vehicle, the Y-axis corresponds to a transverse axis perpendicular to the X-axis and lying in the horizontal plane. The Z-axis is a vertical axis perpendicular to the plane formed by the X and Y axes, it being understood that each of the previously defined axes can be considered an equivalent respective direction.

[0021] In addition, the terms "front" and "rear" refer to the longitudinal direction of the tractor chassis.

[0022] For the purposes of this invention, the term "suspended links" refers to suspended mechanical links comprising a hydropneumatic damping means, located at the rear of the cab, and the terms "non-suspended link" or "articulated link" refer to the non-suspended articulated mechanical link. The suspension system according to the invention therefore does not include a spring damping means.

[0023] The optimal suspension of a cabin must allow roll and pitch movements to be suspended in a measured and controlled manner.

[0024] Thus, according to the invention, the inventors have developed a system for suspending a cabin relative to a chassis in which the suspension of the cabin during pitching motion is ensured by the rotation of said cabin around the unsuspended articulated joint along the transverse axis Y and by the compression of the cylinders of the suspended links respectively located at the rear left and rear right of the tractor cab.

[0025] Furthermore, the suspension of the cabin during the rolling movement is ensured by a power take-off around the non-suspended articulated link along the longitudinal axis X as well as by the compression of the cylinder of the right rear suspended link and the relaxation of the cylinder of the left rear suspended link, or vice versa.

[0026] It is understood within the meaning of the invention that the power take-off of the cabin is only possible from the non-suspended link located at the front of the cabin.

[0027] According to the invention, the compression of the hydraulic cylinders is made possible by means of pressure accumulators fluidically connected to each of the cylinders of the suspended linkages. The pressure accumulators are oleo-pneumatic diaphragm pressure accumulators that ensure a seal between the gas and the oil. Preferably, the accumulators of the invention have a lower installed gas pressure than the installed oil pressure of the hydraulic circuit, in order to be able to return the oil pressure resulting from the compression of a cylinder during, for example, a power take-off of the cab.

[0028] Furthermore, the suspension system according to the invention comprises two conduits fluidly connecting respectively the piston side of the cylinder of each suspended link to the rod side of the cylinder of the other suspended link so as to form a hydraulic interweaving of the cylinders.

[0029] In this way, roll control is ensured by a hydraulic circuit which returns the oil compression pressure of one cylinder to the expansion pressure of the other cylinder in order to limit the expansion movement of the cylinder and therefore the roll movement of the cabin.

[0030] Thus, advantageously and according to the invention, the interlacing of the lines and the pressure accumulators of the suspension system according to the invention makes it possible to generate anti-roll without affecting the pitching motion. According to another advantage of the invention, the hydraulic circuit allows the generation of anti-roll by directing pressure to the cylinders via hydraulic lines, which eliminates the need for a mechanical anti-roll device arranged between the cab and the chassis. In other words, the invention allows for the easy integration of a hydraulic anti-roll device. An "anti-roll device" is understood to be a device designed to limit the rolling motion.

[0031] By interlacing the pipes, we mean a schematic cross-shaped pipe installation; thus, the hydraulic cylinders of the suspended links of the suspension system according to the invention are connected to each other by the crossing of said pipes. Advantageously, the cross-shaped arrangement of the pipes connecting the cylinders developed by the inventors also prevents potential leakage. at the level of the cylinders by acting as an inter-cylinder compensation system. This hydraulic interweaving also helps to maintain the fluid balance in the closed circuit which ensures that the initial position of the cabin is maintained without the addition of a control module, in other words the circuit of this embodiment is self-compensating.

[0032] Advantageously and according to the invention, the non-suspended articulated mechanical link comprises a joint, said joint being a ball joint.

[0033] Thus, the unsuspended link located at the front of the vehicle allows the movement of the cab's suspension system to be taken into account. To this end, the ball joint allows three degrees of freedom for the rotation of the cab around the X, Y, and Z axes.

[0034] Advantageously and according to the invention, the pressure accumulator is fluidly connected to the piston side of said cylinder.

[0035] Thus and according to this advantageous variant, the system evolves under the action of a constant pressure, which allows the suspension system according to the invention to work in equilibrium.

[0036] Advantageously and according to the invention, each cylinder further comprises a second pressure accumulator fluidly connected to the rod side of said cylinder.

[0037] Advantageously, and according to the invention, the suspension system further comprises a stabilizer bar arranged transversely between the two suspended links, said stabilizer bar mechanically connecting the cab and the chassis. Preferably, the stabilizer bar is a Panhard rod. The stabilizer bar connects the chassis to the cab transversely and is positioned longitudinally at the rear of the cab, thus enabling the rear of the cab to be guided transversely. The connection between the stabilizer bar and the cab is of the pivot type, possibly of the elastic type. The connection between the stabilizer bar and the chassis is of the ball joint type, possibly of the elastic type.

[0038] Thus and according to this advantageous variant, the suspension system prevents the yaw movement corresponding to the rotation of the cabin around the vertical axis Z during the pitch or roll phases.

[0039] Advantageously, and according to the invention, the suspension system further comprises at least one position sensor configured to detect the vertical position of the cab relative to the chassis. In one embodiment, said sensor is electrically connected to said suspension system.

[0040] During the mounting of the cabin on the chassis, the cabin is suspended by the suspension system according to the invention. Thus, the cabin is in a predetermined vertical suspension state. This suspension state corresponds to a position called the nominal position of the cabin. This position changes when a user enters the cabin or, more generally, when the cabin is subjected to stress.

[0041] Generally, and for the purposes of the invention, a change in the nominal position of the cabin can be interpreted as a change occurring during the vertical stroke of the piston of a cylinder, beyond a position corresponding to the nominal position of the cabin, during compression or extension along the vertical axis Z. The nominal position of the cabin corresponds to the average position of said cabin over a given period of time. The position sensor can be located on the suspended or unsprung links or even on the stabilizer bar of the suspension system according to the invention.

[0042] The position sensor can be a sensor known to those skilled in the art, such as a wired or cabled sensor. This sensor can be configured to send a signal when it detects a change in the position of the cabin. The sensor signal can be an electrical signal that continuously or periodically provides the vertical position of the cabin relative to the chassis along the Z-axis.

[0043] Thus and according to this advantageous variant, the position sensor makes it possible to detect a change in the nominal position of the cabin with respect to the vertical axis Z and to send a signal associated with this change of position.

[0044] Advantageously and according to the invention, the suspension system further comprises a hydraulic circuit control module, said module being electrically connected to said position sensor and comprising at least one solenoid valve fluidly connected to the pressure accumulators connected to the piston side of each cylinder, said control module being configured to adjust the position of the cabin according to the data received by said position sensor.

[0045] Preferably, the control module may include two solenoid valves arranged in series.

[0046] According to one embodiment of the invention, the control module can be arranged on the cab or on the chassis of the tractor and is electrically connected to the position sensor.

[0047] The control module is configured to acquire angular position data from the position sensor. Furthermore, it is an electronic control module configured to process the received data and convert it into vertical position data for the cabin. The vertical position data can then be compared to the cabin's nominal position so that the control module can decide whether position regulation is necessary.

[0048] This decision can be made by setting a threshold value associated with the nominal position value of the cab. When this threshold value is exceeded, the module controls the cab position regulation by adding or removing oil from the system via the control of one or more solenoid valves.

[0049] The solenoid valve of the control module according to the invention is fluidly connected to the pressure accumulators via a hydraulic line and thus allows oil to be added or removed from the hydraulic circuit.

[0050] Thus and according to this advantageous variant, the control module makes it possible to rectify the oil pressure of the cylinders as a function of the stroke of the cylinders along the Z axis.

[0051] Advantageously and according to the invention, the hydraulic circuit comprises a conduit fluidly connecting the pressure accumulators connected to the piston side of each cylinder.

[0052] Advantageously and according to the invention, the hydraulic circuit includes at least one flow regulator mounted on the line fluidly connecting the pressure accumulators connected to the piston side of each cylinder.

[0053] Thus, according to this advantageous variant, the suspension system makes it possible to prevent sudden movements of the cylinders when adjusting the pressure, thereby improving user comfort.

[0054] The invention also relates to an agricultural tractor comprising a cab mounted on a chassis, said tractor comprising a suspension system characterized in combination by all or part of the characteristics mentioned above or below. List of figures

[0055] Other objects, features and advantages of the invention will become apparent from the following description, given by way of non-limiting example only, and which refers to the accompanying figures in which: • [Fig.1] is a schematic isometric perspective view of the suspension system of a tractor cab according to a first embodiment of the invention. • [Fig.2] is a schematic view representing the arrangement of the system of rear suspension of the vehicle according to the embodiment shown [Fig.1]. • [Fig.3] is a schematic view representing the circuit hy in more detail draulique of the suspension system according to another embodiment of the invention.

[0056] Detailed description of an embodiment of the invention

[0057] In the figures, the scales and proportions are not strictly respected for the purposes of illustration and clarity.

[0058] Identical, similar or analogous elements are designated by the same references in all figures.

[0059] In the entire detailed description that follows with reference to the figures, unless otherwise indicated, each element of the suspension system is described as it is arranged within a tractor.

[0060] Figures 1 and 2 illustrate a first embodiment of the invention, and the [Fig.3] another embodiment of the invention.

[0061] The suspension system 1 of a tractor cab 2 mounted on a chassis 3 is arranged between the cab 2 and the chassis 3. More specifically, the suspension system 1 mechanically connects the cab 2 and the chassis 3 of the tractor along a vertical direction approximated by the vertical axis Z. The chassis 3 extends along a longitudinal direction approximated by the longitudinal axis X, corresponding to the direction of travel of the tractor. The cab 2 extends above the chassis in the same direction.

[0062] The suspension system 1 of the cabin 2 relative to the chassis 3, includes vertical links mechanically connecting the lower part 2a of the cabin 2 with the upper part 3a of the chassis 3.

[0063] More particularly, the suspension system 1 comprises a non-suspended articulated link 10 arranged at the front of the cab 2 and two suspended links 20 arranged at the rear of the cab, said links 10 and 20 being longitudinally opposed along the X axis of the chassis 3. The two suspended links 20 are arranged opposite each other and spaced along the transverse axis Y. The suspension system 1 of the described embodiment thus has three points of attachment of the cab to the chassis, two of which are suspended.

[0064] The non-suspended articulated link 10 includes a joint 11 allowing the cabin 2 to take rotational movement along the X and / or Y axes. As such, the link 10 includes a ball joint 11.

[0065] The suspended joints 20 are double-jointed joints, each comprising a double-acting hydraulic cylinder 21. The hydraulic cylinder 21 comprises a rod 22 connected to a piston 23 and is further fluidly connected to at least one pressure accumulator 40. Each hydraulic cylinder 21 of the suspended joints 20 has a rod end 21a and a piston end 21b.

[0066] The suspension system 1 according to one embodiment thus comprises a hydraulic circuit 60 in which two lines 21c fluidly connect respectively the rod side 21a of a first cylinder 21 to the piston side 21b of a second cylinder 21. A portion of the hydraulic circuit 60 thus forms an inter-cylinder connection between the cylinders 21 of the two suspended links 20. The hydraulic crossover 24 is thus formed by the two lines 21c and makes it possible to form a suspension system integrating integrated hydraulic management of anti-roll via the hydraulics of the circuit 60.

[0067] The cab suspension system 1 further includes a control module 50 for the hydraulic circuit 60. In the described embodiment, the control module 50 comprises two solenoid valves 51, 52 mounted in series and fluidly connected to a line 4L. When a force is exerted on the cab 2, the suspension system 1 will adjust the position of the cab so that it returns to its initial position. For this, the control module 50 will control the fluid exchanges, and in particular the oil exchanges of the hydraulic circuit 60.

[0068] Advantageously, when a power take-off at the joint 11 of the unsuspended link 10 causes the cabin 2 to rotate about the longitudinal axis X, for example, a cylinder 21 of a first suspended link 20 will go into compression while the cylinder 21 of a second suspended link 20 will reciprocally go into expansion. Consequently, the hydraulic pressure accumulator 40, being an oleopneumatic device fluidly connected to the cylinder in compression, will receive an oil pressure greater than the installed pressure of the gas it contains. This gas being compressible, such as nitrogen, it will thus absorb the pressure increases of the fluidic system and expel the excess oil to the lines 21c, in order to compensate for the expansion of the other cylinder and restore hydraulic balance between each of the cylinders 21 of each of the suspended links 20.This balance is further reflected in the return of cabin 2 to a comfortable position for the user.

[0069] The suspension of movement is made possible via the pressure accumulator 40. During a pressure increase associated with a bump, for example, the gas will compress until the pressures in the accumulator 40 equalize between the gas and the oil. The compression of the gas will cause the accumulator to fill with oil, and thus generate a movement of the cylinder.

[0070] The reduction of roll is achieved by an exchange of oil between the cylinders 21 by means of the hydraulic interlock 24. Under the effect of compression, there will be an absorption of flow by an accumulator on the one hand and a vacuum on the opposite cylinder on the other hand, the balance of the oil pressures will decrease the gas pressure which will allow the expansion of the cylinder and the release of oil towards the opposite cylinder.

[0071] In one embodiment, the suspension system 1 further comprises a stabilizer bar 30 arranged obliquely in the transverse direction between the two unsprung links 20. The stabilizer bar 30 is connected to both the chassis 3 and the cab 2 and eliminates the yaw movement corresponding to a rotation of the cab about the vertical axis Z. The suspension system 1 may include a means for detecting the angular position of the cab 2 relative to the chassis 3 and determining the position, referred to as the nominal position of the cab 2, which corresponds to the average of the angular position of the cab 2 over a given time, without taking shocks into account. The control module 50 processes and converts the angular position data from the sensor into data indicating the vertical position of the cab 2 relative to the chassis 3. This acquired position data corresponds to the stroke of the cylinders.The 50 control module is also configured to average the position data acquired on . a period of time and thus be able to determine a nominal position of the cabin. The module allows a comparison of the position data value with the value of a predetermined nominal position. A threshold value can be pre-recorded so that the control module can compare this average position value of cabin 2 with the previously recorded or determined nominal position value of cabin 2. According to the invention, the control module 50 can be configured to readjust the cabin position relative to the stroke of the cylinders 21 via the solenoid valves 51, 52 based on a threshold value higher or lower than the nominal position value of cabin 2.For example, when a stress exerted on the cabin causes a compression greater than half the stroke of a cylinder 21, the adjustment and return to equilibrium or to the nominal position of the cabin 2 will be able to be carried out by the control of the solenoid valves 51,52. .

[0072] The oil level of the hydraulic circuit 60 can thus be readjusted by a set of two solenoid valves in series, the first of which allows oil to be added to the system and the second of which allows excess oil to be removed.

[0073] The solenoid valves can be fluidly connected to a line 4L The line 41 being fluidly connected to an accumulator 40 and said accumulator 40 being fluidly connected to a cylinder 21 of each of the suspended links 20.

[0074] In addition, system 1 may also include flow regulators 53 mounted on the line 41 to prevent excessively rapid vertical movement of the cylinders during the circulation of oil in the circuit 60.

[0075] According to the embodiment described, the suspension system 1 not only compensates for the theoretical leakage rates that may occur in the circuit 60 at the level of the cylinders 21, but also generates anti-roll in an integrated manner and without affecting the pitch phase, thus enabling optimal cabin suspension.

[0076] Fig. 1 illustrates in isometric perspective the arrangement of a suspension system 1 according to an embodiment of the invention where said system 1 comprises a stabilizer bar 30 arranged between the two suspended links 20.

[0077] In this embodiment, the articulated, unsuspended joint 10 includes a joint 11 which is a ball joint. This ball joint allows the cabin 2 to rotate about the ball joint along the X and Y axes. In this configuration, the stabilizer bar 30 prevents yaw movement corresponding to the rotation of the cabin about the Z axis.

[0078] Fig. 2 schematically illustrates a view of the rear of the cab 2 explaining in more detail the configuration of the suspension system 1 at the rear of the cab according to the embodiment of Fig. 1.

[0079] In the embodiment shown in Figures 1 and 2, the suspension links 20 and the stabilizer bar 30 form vertical links mechanically connecting a lower part 2a of the cab 2 with an upper part 3a of the tractor chassis 3. Furthermore, the suspension links 20 and the stabilizer bar 30 include ball joints on either side.

[0080] Figure 3 schematically illustrates another embodiment of the invention. This figure illustrates more particularly the hydraulic control of the cylinders 21 of the suspension system 1, according to which the control of the circuit 60 is carried out via the control module 50 comprising the two solenoid valves 51 and 52. The solenoid valve 51 has the function of removing oil from the circuit 60 when it is in the actuated state. In the closed state, the solenoid valve 51 includes a check valve allowing the passage of oil from the solenoid valve 52 only in one direction to the hydraulic circuit 60. The solenoid valve 52 is fluidly connected to the solenoid valve 51 and has the function of distributing oil to the circuit 60 when it is in the actuated state. In the closed state, solenoid valve 52 returns the oil to the level of an oil reservoir.

Claims

Claims

1. System (1) for suspending a cabin (2) of an agricultural tractor on a chassis (3) of the tractor, said chassis (3) extending in a longitudinal direction corresponding to the direction of movement of the tractor, said cabin (2) extending above the chassis (3), said system (1) comprising vertical mechanical connections connecting said cabin (2) and said chassis (3), said suspension system (1) being characterized in that said vertical mechanical connections comprise at least: • an unsuspended articulated mechanical connection (10), the articulation (11) of which is a ball joint, said connection (10) being arranged longitudinally at the front of the cabin (2);• two suspended mechanical connections (20) each comprising a double-acting hydraulic cylinder (21), said cylinder (21) having a piston side (21b) and a rod side (21a), said suspended connections (20) being arranged longitudinally at the rear of the cabin (2) and spaced transversely opposite one another; and in that it comprises a hydraulic circuit (60) comprising, for each cylinder (21), at least one pressure accumulator (40) fluidly connected to said cylinder (21), and two pipes (21c) fluidly connecting and respectively the piston side (21b) of the cylinder (21) of each suspended connection (20) to the rod side (21a) of the cylinder (21) of the other suspended connection (20) so as to form a hydraulic intersection (24) of the cylinders.;

2. System according to claim 1, characterized in that the pressure accumulator (40) is fluidically connected to the piston side (21b) of said cylinder (21).

3. System according to claim 2, characterized in that each cylinder (21) further comprises a second pressure accumulator fluidly connected to the rod side (21a) of said cylinder (21).

4. System according to one of claims 1 to 3, characterized in that it further comprises a stabilizer bar (30) arranged in the transverse direction between the two suspended links (20), said stabilizer bar (30) mechanically connecting the cabin (2) and the chassis (3).

5. System according to claim 4, characterized in that it further comprises a position sensor configured to detect the vertical position of the cabin (2) relative to the chassis (3).

6. System according to one of the preceding claims, characterized in that it further comprises a control module (50) of the hydraulic circuit (60), said module (50) being electrically connected to said position sensor and comprising at least one solenoid valve fluidly connected to the pressure accumulators connected to the piston side of each cylinder, said control module being further configured to adjust the position of the cabin according to the data received by said position sensor.

7. System according to one of claims 2 to 6, characterized in that the hydraulic circuit (60) comprises a pipe (41), said pipe (41) fluidly connecting the pressure accumulators (40) connected to the piston side (21b) of each cylinder (21).

8. System according to claim 7, characterized in that the hydraulic circuit (60) comprises at least one flow regulator (53) mounted on the pipe (41).

9. Agricultural tractor comprising a cabin (2) mounted on a chassis (3) characterized in that it comprises a suspension system (1) according to one of claims 1 to 8 arranged between said cabin (2) and said chassis (3).

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