IES80403B2 - A bale wrapping apparatus having apparatus for gripping and cutting film - Google Patents

Abstract

A bale-wrapping machine having a chassis (1), a tipping platform (4) connected to the chassis, means for wrapping a bale (14) placed on the tipping platform, and a device for gripping and cutting film (17) mounted on the chassis, said device comprising a gripping assembly having gripping means moveable from a closed position in which the gripping means is adapted to grip the plastics film to an open position in which the gripping means is adapted to release the film, cutting means (34) adapted to cut the gripped film, and means for closing (24,25) and means for opening (40) the gripping means, wherein the means for closing the gripping means and retaining the gripping means in the closed position comprises a hydraulic cylinder and piston (24,25) together with means to supply hydraulic fluid to a first end of the cylinder, and the means for opening the gripping means comprises means to supply hydraulic fluid to the other (second) end of the cylinder, and wherein the hydraulic supply means to the first end of the cylinder is controlled by an electrically-operated valve (48) controlled by a manually operable switch (59).

Description

A BALE WRAPPING APPARATUS HAVING APPARATUS FOR GRIPPING AND CUTTING FILM The present invention relates to a bale wrapping machine having apparatus for gripping and cutting film in the wrapping of an object with the film. The term film is intended to include sheeting, web material, strip material and the like sheet material suitable for wrapping objects. The invention is particularly suitable for use with machines for wrapping bales, such as large round bales, of silage, hay, straw and the like (hereinafter referred to as fodder) with a plastics film. Examples of bale wrapping machines of the kind described are disclosed in U.K. Patent Specifications Nos. 2 191 984 A, 228 246 and 2 241 916, the contents of which are incorporated herein by way of reference.

Bale wrapping machines of the kind described comprise a wheeled chassis which may be towed by a tractor. The chassis carries a tipping platform which, in turn, supports a turntable. The turntable is rotatable about a vertical axis. The turntable carries a pair of spaced rollers each of which rotates about a horizontal axis. An endless belt is stretched between the rollers and rotates with the rollers. In order to wrap a large round bale of fodder material with plastics film, the round bale is lifted onto the turntable by meansiof lifting arms. The bale rests on the endless belt. The free end of a roll of plastics film is attached to the bale and the turntable is then rotated about a generally vertical axis to cause the sheet of film to be wrapped around the bale. However, if no movement of the bale about its longitudinal axis were to occur the bale would merely be wrapped - 2 with a single band having the thickness of the width of the plastics film. However, on each rotation of the turntable the endless belt is caused to move for a predetermined distance which, in turn, causes the bale to roll about its surface. This rolling of the bale on the belt allows a new area of bale to be wrapped by the film on each rotation of the turntable, thus eventually achieving a complete covering of the bale with a substantial degree of overlap of the plastics film.

The invention is concerned with apparatus which is intended to grip the free end of the film and to bring the film around the bale during the initial revolutions of the turntable, usually the first two revolutions. The apparatus then releases the film to allow wrapping to continue. At the end of the wrapping operation the apparatus again comes into contact with the film to grip the film and to cut the film so as to release the film from the bale. The film is then held in the gripping device ready for attachment to the next bale to be wrapped.

EP 0 367 529 A discloses an automatic round bale wrapper incorporating a device for gripping and cutting the plastics film in which the device is operated by a winding mechanism which tensions the gripping and cutting device step-wise at each revolution of a round bale table of the bale wrapper. Mechanical gripping and cutting devices of this kind are complicated in design and do not lend themselves to addition as a kit to existing bale wrapping machines.

U.K. Patent Specification No. 2 241 916 describes a bale-wrapping machine having a chassis, a tipping platform pivotally connected to the platform, a turntable mounted for rotation upon the platform and a conveyor means on the turntable such that a bale of fodder placed on the turntable may be rotated about both substantially horizontal and substantially vertical axes, a film dispensing means spaced from the turntable, and a device for gripping and cutting film mounted on the turntable, said device comprising a gripping assembly having gripping means moveable from a closed position in which the gripping means is adapted to grip the plastics film to an open position in which the gripping means is adapted to release the film, cutting means adapted to cut the film on closure of the gripping means, and means for closing - 3 and opening the gripping means, wherein the means for opening the gripping means comprises an electrically operated linear actuator.

U.K. Patent Specification No. 2 241 916 also describes a device for gripping and cutting film in the wrapping of an object with the film comprising a gripping assembly having gripping means moveable from a closed position in which the gripping means is adapted to grip the plastics film to an open position in which the gripping means is adapted to release the film, cutting means adapted to cut the film on closure of the gripping means, and means for closing and opening the gripping means, wherein the means for opening the gripping means comprises an electrically operated linear actuator, and the means for closing the gripping means comprises spring means which are adapted to be tensioned by the linear actuator on opening of the gripping means and subsequently released, by movement of the linear actuator, to close the gripping means and simultaneously to cut the film. Suitably, the linear actuator has associated therewith signal means, the arrangement being such that on receipt of a first signal an actuator rod of the linear actuator is caused to move from a retracted position to an extended position to open the gripping means and simultaneously to tension the spring means, on receipt of a second signal by the linear actuator the actuator rod is caused to retract to an intermediate position, the spring means being maintained in a tensioned state by latch means, and on receipt of a third signal by the linear actuator the actuator rod is caused to retract further to trip the latch means and release the spring means.

The device of U.K. Patent Specification No. 2 241 196 has been used successfully. However it requires a substantial number of both electrical and mechanical components which require maintenance if malfunctioning is to be avoided. There is a need for a simpler structure of apparatus for gripping and cutting the film, with the option of automatic operation of the apparatus.

In use of the device of U.K. Patent Specification 2 241 196, the gripping and cutting mechanism is activated at a desired point during the tipping operation. However the tipping operation continues and - 4 there is a risk that film may not be gripped and cut before the bale is tipped off.

The invention provides a bale-wrapping machine having a chassis, a tipping platform connected to the chassis, means for wrapping a bale placed on the tipping platform, and a device for gripping and cutting film mounted on the chassis, said device comprising a gripping assembly having gripping means moveable from a closed position in which the gripping means is adapted to grip the plastics film to an open position in which the gripping means is adapted to release the film, cutting means adapted to cut the film on closure of the gripping means, and means for closing and means for opening the gripping means, wherein the means for closing the gripping means and retaining the gripping means in the closed position comprises a hydraulic cylinder and piston together with means to supply hydraulic fluid to a first end of the cylinder, and the means for opening the gripping means comprises means to supply hydraulic fluid to the other (second) end of the cylinder, and wherein the hydraulic supply means to the first end of the cylinder is controlled by an electrically-operated valve controlled by a manually operable switch.

Suitably the means for opening the gripping means is automatically activated at a predetermined time. Preferably the means to supply hydraulic fluid to the first end of the cylinder is connected in a hydraulic circuit to hydraulic means for tipping the tipping platform.

In a preferred arrangement the hydraulic circuit includes control means to stop tipping movement of the tipping platform while the gripping means is moved from the open to the closed position and the film is cut.

In a more preferred arrangement the hydraulic circuit is controlled by electrically-operated valves and means are provided to monitor tipping movement of the tipping platform and to generate a - 5 signal observable by an operator of the machine at a desired tipping angle.

Preferably the means for opening the gripping means comprises a hydraulic accumulator connected to the second end of the cylinder. The accumulator acts in a manner analogous to that of a spring to return the piston to the first end of the cylinder.

Suitably the hydraulic accumulator comprises an inner and an outer chamber separated by a flexible diaphragm, the inner chamber being sealed and containing a compressible fluid and the outer chamber being connected to the hydraulic cylinder.

In an alternative embodiment, the cylinder is reversed and the means for closing the gripping means comprises a hydraulic accumulator.

In a preferred arrangement the gripping means comprises a moveable head attached to the piston of the hydraulic cylinder and a spring-loaded buffer against which the head buts in the closed position of the gripping means.

Preferably the cutting means comprises a fixed blade alongside and/or in front of the buffer, such that the film is pushed by the moveable head against the blade to cut through the film before closure motion of the head is complete.

Preferably the hydraulic supply means and/or the hydraulic circuit are controlled by a joystick.

The invention extends to a bale wrapping machine substantially as described herein with reference to Figures 1 to 4 of the accompanying drawings, and incorporating the device of Figures 5 and 6 and the hydraulic, electrical and control system of Figures 7, 8 and 9 respectively.

The invention provides a cut and start unit for a baling machine which has substantially less mechanical parts than those of the prior - 6 art and which is amenable to automatic operation, particularly to halt tipping movement of the tipping platform while the gripping means are being closed and the film is being cut.

One embodiment of the invention is hereinafter described with reference to the accompanying drawings, wherein: Figures 1 to 4 show a side elevation of a bale wrapping machine fitted with the device of the invention, the bale wrapping machine being shown at different stages of its operation; Figure 5 is a side perspective view of a film gripping device of the type used in the machine of the invention shown in the fully retracted position; Figure 6 is a side view of the device of Figure 5 opposite to the view of Figure 5.

Figure 7 is a diagrammatic plan of the hydraulic system of the wrapping machine; Figure 8 is a diagrammatic plan of the electrical system of the wrapping machine; Figure 9 is a diagrammatic representation of the hydraulic valve controls for the system of Figure 7; Referring firstly to Figures 1 to 4 of the drawings these show a bale wrapping machine of the kind described in our U.K. Patent Specifications Nos. 2228246 and 2241946.

The bale wrapping machine comprises a chassis 1 having a pair of wheels 2. The chassis is provided with a hitch 3 for attachment to a tractor. A tipping platform 4 is mounted on the chassis 1. As best seen in Figures 3 and 4 the tipping platform is pivotally connected to a bracket 5 at the rear of the chassis 1 such that the tipping platform may be tipped from the horizontal position shown in Figures 1 and 2 to the fully tipped position shown in Figure 4. - 7 A turntable 6 is mounted on the platform 4. The platform 4 is provided centrally with a main bearing which is bolted onto the platform. The main bearing carries a central spindle 8 of the turntable 6. A hydraulic feed line extends through the longitudinal axis of the spindle. A hydraulic rotary coupling 92 is fitted at the base of the spindle and allows hydraulic fluid to be passed to and from the hydraulic cylinder 24 of the cut and start device without limiting the rotational freedom of the turntable 6. (Such a rotary coupling is commercially available from RACCORDS GAUTIER of Romeny sur Marne, France under model No. 617J). The underside of the turntable 6 is fitted with wheels 9 which are adapted to run upon the upper surface of the tipping platform 4, as the tipping platform rotates. The platform 6 has a superstructure 10 on which are mounted a pair of spaced rollers 11. The rollers are mounted for rotation about horizontal axes. An endless belt 12 (see Fig. 4) is mounted rotationally about the rollers. The superstructure 10 is also provided with outwardly inclined arms 13 which define a cradle which is adapted to receive a large bale 14 of silage or other fodder for wrapping. The bale 14 is lifted into the cradle by means of a hydraulically-operated lifting arm (not shown) which extends laterally from the machine. Such lifting arms are well known. When in the cradle, the bale 14 is carried on and is rotated by the belt 12. The top ends of the arms 13 are provided with rollers 18 which assist in positioning the bale 14 in the cradle.

Forwardly of the chassis 1 is mounted an upright 15 on which is mounted a film dispensing system 16. The dispenser system 16 includes a known dispenser and pretensioning unit through which sheeting of plastics film 17 is fed and stretched. A film push down arm which is operated by a hydraulic cylinder may also be mounted on upright 15.

Such devices are well known and act to help bunch the film so that it has a width of 2-15 mm. This action complements the gathering action of the cut and start device of the invention.

The film handling device of the invention is adapted to grip the free end of sheeting 17 and to wrap the sheeting around the bale 14 during the first two revolutions of the turntable 6. By this stage the film will have frictionally attached itself to the bale. The device - 8 then releases the sheeting which continues to wrap around the bale until the bale is fully wrapped. At the end of the wrapping step, the device again grips the sheeting 17, cuts the sheeting and holds the cut end of the sheeting ready for the next bale.

The device of the invention is shown in more detail in Figures 5 and 6 and comprises a main frame 20 constructed from steel box section. The frame 20 is provided at each end with brackets 22,23 by means of which the device is mounted between the pair of arms 13, such that the device extends transversely of the cradle (see Figs. 1 and 2).

The main frame 20 has positioned thereon a hydraulic cylinder 24 which is aligned along the length of longitudinal member 22. The cylinder 24 is a conventional hydraulic cylinder, having an extendable piston 25.

A cylindrically-shaped boss head 26 is attached to the piston 25. Attached at the end of the main frame 20 opposite the cylinder 24, is a bracket 27. Mounted on bracket 27 is a buffer assembly 28. The buffer assembly 28 comprises a retractable plunger 29 which extends through an aperture in the bracket 27. The retractable plunger 29 is held in place by a knob 30. Knob 30 allows retraction of plunger 29, as it is shaped so as not to snag film which contacts it. The plunger 29 has a buffer 31 mounted on its free end. A coil spring 32 is mounted on the plunger 29. A split pin 33 extends through an aperture in the plunger 29 and holds the spring 32 in place between the buffer 31 and the bracket 27. The hydraulic cylinder 24, together with its extendable piston 25, and the buffer assembly 28 form a gripping assembly which will be described in detail below.

The main frame 20 also has mounted thereon a blade 34 which is held by a bracket 35. The blade is parallel to the main frame 20 and is mounted alongside it, beside the buffer 31 in the unretracted position shown in Figures 5 and 6. A U-shaped guide member 36 is attached to the device so that one limb 37 of the guide member 36 is attached to the blade 34 while the other limb 38 is attached to the main frame 20. As can be seen from the perspective of Figure 5 the - 9 guide member 36 is angled and extends above the cylinder 24 and the plunger assembly 28, providing a guide surface towards the cutting edge 39 of blade 34 which is inclined upwardly as shown in Figures 5 and 6.

The hydraulic cylinder 24 has attached thereto a hydraulic feed line 41 at one end and a hydraulic accumulator 40 at the other (second) end. The hydraulic accumulator 40 is a conventional device having a bladder arrangement (not shown) and being filled with gas. Pressure of hydraulic fluid on the bladder causes the gas within the accumulator 40 to be compressed. The cut and start action of the device will now be described.

The piston 25 is extended by the supply of pressurised hydraulic fluid through hydraulic feed line 41. The boss head 26 on the piston 25 and the buffer 25 (made of rubber) are aligned in opposing directions so that on extension of the piston 25, the piston 25 abuts the buffer 31. This gives a gripping action between the boss head 26 and the buffer 31.

In the position of Figure 5 the buffer assembly 28 is arranged so that the buffer 31 extends past the cutting edge 39 of the blade 34. Thus on extension of cylinder 25 in the position shown in Figure 4 the film 17 which extends between the boss head 26 and the buffer 25 will be bundled up until it is eventually gripped between these opposing parts. As described above the device may be aided by a hydraulically operated push-down arm. Continued extension of the cylinder 25 will cause the boss head 26 to apply pressure to the buffer assembly 28 through buffer 31. This causes compression of the spring 32 as plunger 29 retracts. The spring 32 maintains the gripping action while allowing movement of the gripped film 17. The gripped film 17 also moves, being held between the buffer 31 and the boss head 26. The film 17 while retained in this grip is moved into the area between the guide 36 and the blade 34. Continued movement of the film by extension of the cylinder 25 together with the tautness of the film 17, which is held in a tensile state for wrapping, causes the film to be sheared by blade 34. Guide 26 ensures the film is sheared by forcing the film 17 onto the cutting edge 39 of the blade 34. The film 17 is thus sheared quite close to the position in which it is held. Blade 34 is located so as to shear the film 17 at a position between the bale 14 which has been wrapped and the position in which it is gripped by the assembly described above. The film 17 extending from the dispensing system 15 is retained by the gripping device to begin the next cycle. Two opposing rails 90 and 91 are provided on the main frame 20. These provide a sliding surface for the film 17 and direct the bundled film under the U-shaped guide 36.

While piston 25 is being extended hydraulic fluid is forced into the hydraulic accumulator 40 which pressurises the gas contained therein in a conventional manner. On release of the pressure extending piston 25, the reservoir of pressurised gas stored in the accumulator 40 causes the piston 25 to retract to its open position by forcing hydraulic fluid from the accumulator into the cylinder reversing its movement, thus resetting the cut and start assembly for the next required shearing action. This resetting action is rapid.

If it is required to supply electrical current from the tractor battery to any electrical components which may be added to the turn-table 6, a pair of slip rings may be attached to the main spindle (as shown in Figures 15 and 16 of GB 2 241 916 and as described with reference thereto) to provide an electrical supply without limiting the rotational movement of the turn-table 6.

Referring now to Figure 7 which shows a diagrammatic representation of the hydraulic circuit of the bale wrapping machine, the hydraulic oil supply line 42 supplies pressurised hydraulic fluid (from an agricultural tractor) to the bale wrapping machine. The supply line firstly feeds a bank of hydraulic spool valves 43. One valve 44 controls the hydraulic motor 45 which operates the turntable 6 and belt 12. A return line 46 from the hydraulic motor 45 is also provided. The respective functions of the lines 45 and 46 may be reversed to reverse the direction of rotation.

A second valve 47 controls the hydraulic fluid supply to a six port solenoid diverter valve 48. The diverter valve 48 in turn - 11 controls supply of the hydraulic fluid to each of the hydraulic cylinder of the film push-down arm 49, the hydraulic cylinder 50 for tipping the tipping platform 4 and the cut and start hydraulic cylinder 24. The cylinders 49 and 50 are connected to the same pair of ports on the diverter valve 48.

A third valve 52 provides an independent control for the lift arm cylinder 51, (the lift arm is for mounting a bale on the turn-table 6). All the respective hydraulic cylinders have return lines which ultimately return the hydraulic fluid to the tractor through main return line 53. A non return (one-way) valve 54 is fitted to the main return line 53.

A solenoid poppet valve 55 is fitted on the hydraulic line 56 from the hydraulic supply line 41 to the return line 53 which by passes the valves 48 and 43.

The hydraulic supply line 41 to the cylinder 24 includes a rotary union 92 which allows flow of hydraulic fluid from the cylinder 24 (and allows pressure to be maintained in the cylinder 24) even when the turn-table 6 is revolving.

Referring now to Figure 8 the electrical circuit will now be described.

A bale wrap monitor 57 is programmed to monitor the number of rotations of the bale 14 desired and to give an electrical signal to an alarm (not shown) which sounds to indicate to the machine operator that the programmed number of revolutions of the turn-table 6 have been executed.

The monitor 57 also is programmed to give an electrical signal to the solenoid poppet valve 55 after a predetermined revolution (normally the second) of the turn-table 6. This releases the hydraulic pressure in supply line 41 to cylinder 24 and causes the gripped film 17 to be released by the pressure in the accumulator 40 which forces hydraulic fluid back into cylinder 24 causing it to retract as described above. - 12 A joystick control 58 is located in the cab of a tractor within reach of the operator. The joystick has a microswitch 59 located thereon. Activation of the microswitch 59 causes the oil to be diverted from hydraulic tipping ram 50, to the cylinder 24 of the cut and start device thus severing the film 17.

The bale wrap monitor 57 is connected via a six-way electrical connector 60 to the microswitch 59, the rotary sensor 93, the solenoid poppet valve 55, and the six port solenoid diverter valve 48, and (indirectly) to the positive terminal of the 12 volt DC (battery) supply 94 of the tractor, and is also negatively earthed by earth 95 to the vehicle body. The circuit is protected by an 8 amp fuse 96.

Referring to Figure 9 of the operation of the machine will now be described.

The joystick control 58 is a dual axis valve actuator movable in the directions indicated as A,B,C and D. The joystick control 58 has two cables (not shown) extending through cable sleeves 97 and 98 and which operate the valves 52 and 47.

Movement of the joystick 58 in direction A operates hydraulic spool valve 47 which in turn operates the hydraulic ram 50 for tipping the tipping platform 4 (via the diverter valve 48). Direction C reverses the tipping action returning the tipping platform 4 to its normal operating position. Direction B gives reverse rotation of the turn-table 6, through valve 44 while direction D rotates the turn-table in the normal wrapping direction. A single lever control 80 controls the lift arm for loading a bale 14 onto the turn-table 6 through valve 44 in a similar manner.

Normal operation of the device is as follows : In order to prepare the bale wrapping machine for the wrapping of a bale 14, the turntable 6 is rotated to a position in which the film handling device of the invention is located at the front of the machine. The free end of the roll of plastics film 17 is held by the - 13 cut and start device locating the sheet 17 in the gripped position on the cut and start device. The turntable 6 is then rotated anticlockwise through 90° to the position shown in Figure 1 by movement of the joystick in the C direction. A bale 14 is then lifted into the cradle of the machine by means of a lifting arm (not shown) by operation of the single control lever 80. The turntable 6 is then rotated clockwise by operation of the joystick in direction D. This causes the film handling device of the invention to circle the bale 14 to commence wrapping the film 17 around the bale.

The sensors used to determine when to open the gripping means are as described with reference to Figure 13 of GB 2 241 916. During the chosen turn-table revolution (revolution No. 2 normally), the bale wrap monitor 57 sends an electrical signal to the solenoid poppet valve 55 causing it to open and allow release of hydraulic fluid pressure from the cut and start device by expansion of the gas reservoir in the accumulator. The oil forced out of the accumulator by the expanding gas causes the cut and start device to open and thus release the film 17 as described above. Release of the film 17 is very quickly done.

By this stage the film has already attached itself to the bale 14 and the turntable 6 continues to revolve to completely wrap the bale in the plastics film.

When the alarm sounds (as described above) to indicate the bale 14 has been wrapped as desired the turn-table 6 is stopped with the cut and start device located to the front of the machine as shown in Figure 2, the joystick 58 is operated in direction A to tip the tipping platform 4. When the film 17 has been gathered up fully (but not gripped) by the cut and start device (and the push down arm) the microswitch 59 on the joystick 58 is operated. This sends a signal to six-port solenoid valve 48 causing it to close one port and shut off supply of further hydraulic fluid to the hydraulic ram 50 for tipping of tipping platform 4, and opening another port to divert oil to cut and start cylinder 24. The cylinder 24 extends and the film 17 is gripped and cut as described above. The turn-table 6 is in the Figure 3 position. The microswitch 59 is released, causing resumption of the tipping cycle by supplying hydraulic fluid to the ram 50 but - 14 maintaining the pressure in the cylinder 24 to hold it in the extended position until the bale 14 is tipped off, having been wrapped (the position shown in Figure 4).

The bale wrap monitor 57 may also be used to send a signal to the cut and start cylinder 24 during the tipping cycle to effect automatic operation of the grip and cut action. A tipping sensor may be used to sense tilting of the platform (by a magnet or as described with reference to Figure 14 of GB 2 241 916) and in turn to send a signal to the bale wrap monitor 57 which then activates six port solenoid valve 48, interrupting the tipping cycle and operating the grip and cut mechanism. After a set time delay (within which period the gripping and cutting movement action is completed) the tipping action is resumed. Alternatively a further sensor may be used to indicate when the gripping and cutting movement is complete, and to resume the tipping action.

At any stage the operator may operate the grip and cut by activating the microswitch 57, and operating the joystick 58 in the relevant direction.

The device may also be used in conjunction with a bale wrapping machine where the film dispensing system revolves about the bale so as to wrap it and there is no rotatable turn-table. In general the machine provides for relative rotational movement between the film dispensing means and the bale.

The gripping and cutting device of the invention may be built integrally with the bale-wrapping machine. It is also suitable for supply as a kit for attachment to existing machines.

Claims (5)

1. A bale-wrapping machine having a chassis, a tipping platform connected to the chassis, means for wrapping a bale placed on the tipping platform, and a device for gripping and cutting film mounted on the chassis, said device comprising a gripping assembly having gripping means moveable from a closed position in which the gripping means is adapted to grip the plastics film to an open position in which the gripping means is adapted to release the film, cutting means adapted to cut the gripped film, and means for closing and means for opening the gripping means, wherein the means for closing the gripping means and retaining the gripping means in the closed position comprises a hydraulic cylinder and piston together with means to supply hydraulic fluid to a first end of the cylinder, and the means for opening the gripping means comprises means to supply hydraulic fluid to the other (second) end of the cylinder, and wherein the hydraulic supply means to the first end of the cylinder is controlled by an electrically-operated valve controlled by a manually operable switch.

2. A machine according to claim 1 wherein the means for opening the gripping means is automatically activated at a predetermined time.

3. A machine according to claim 1 or 2 wherein the means to supply hydraulic fluid to the first end of the cylinder is connected in a hydraulic circuit to hydraulic means for tipping the tipping platform.

4. A machine according to claim 3 wherein the hydraulic circuit includes control means to stop tipping movement of the tipping platform while the gripping means is moved from the open to the closed position and the film is cut.

5. A machine according to claim 3 or claim 4 wherein the hydraulic circuit is controlled by electrically-operated valves and means are provided to monitor tipping movement of the tipping platform and to generate a signal observable by an operator of the machine at a desired tipping angle.