GB2163238A

GB2163238A - Hydraulic drive system for vehicle-mounted mixer drum

Info

Publication number: GB2163238A
Application number: GB08421003A
Authority: GB
Inventors: Albert Goldsmith
Original assignee: Northern Engineering Industries PLC
Current assignee: Rolls Royce Power Engineering PLC
Priority date: 1984-08-17
Filing date: 1984-08-17
Publication date: 1986-02-19
Also published as: GB8421003D0

Abstract

A drive system 10 for a vehicle-mounted mixer drum 12 has a diesel engine 14 which drives a variable-displacement hydraulic pump 16 which in turn drives the drum 12 through a hydraulic turbine 18 and a transmission 22. The engine 14 is controlled by a foot pedal 26 or a lever 28 via a Bowden cable. The pump 16 is controlled by an electromechanical device 30 connected to the pilot valve controlling the displacement of the pump 16. The device 30 is operable by levers 34, 36 or by an electronic circuit arrangement 38. The arrangement 38 receives a feedback signal from a drum speed sensor. During a loading operation, the speed of the engine 14 is set to be sufficient to rotate the drum 12 (when loaded) at say 10 RPM and the arrangement 38 is switched on to maintain automatically the speed of rotation of the drum 12 at 10 RPM. Following loading, the arrangement 38 is set to maintain the speed of the drum 12 at say 1 RPM even when the vehicle is travelling to a site. <IMAGE>

Description

SPECIFICATION Drive systems for vehicle-mounted mixer drums This invention relates to drive systems for vehicle-mounted mixer drums.

The drive system (hereinafter referred to as "a drive system system of the type referred to") for vehicle-mounted mixer drums comprises a motor, a variable-displacement hydraulic pump driven by the motor, a hydraulic turbine driven by the pump and a transmission connecting the turbine to the drum. The motor of a drive system of the type referred to is the drive motor of the vehicle or is a separate motor mounted on the mixer drum support system and such drive or separate motors are usually diesel engines. The speed of rotation of the drum is dependent upon both the speed of the motor and the displacement of the pump which, in a drive system of the type referred to, are controlled by first and second levers, respectively. Such levers are usually located at the rear of the vehicle and can be manipulated by the operator to control the speed of rotation of the drum.Often repeater levers are located in the cab of the vehicle also, although, when the motor is the drive motor of the vehicle, the conventional accelerator pedal is used to control the speed of the motor while the repeater lever is used to control the displacement of the pump.

Such control of a drive system of the type referred to is essential during the discharge of material from the mixer drum on a site so that the operator can properly control the rate of discharge of material from the drum. However, such control of a drive system of the type referred to has disadvantages when used during the loading and transporting operations when constant speeds of rotation of the drum are preferred, typically 10 to 1 2 RPM and 1 to 2 RPM, respectively.

During loading of the drum with material, the increasing amount of materials in the drum causes rapid changes in the load experienced by the motor (particularly if a separate motor is used since it is usually smaller than the vehicle motor). Thus, the operator has to try to compensate for such changes which tends to lead to an excessive use of fuel, the generation of noise and additional wear to moving parts.

When the motor is the drive motor of the vehicle, the speed of rotation of the drum can fluctuate considerably during the transporting operation whilst the vehicle is travelling to a site. During this transportation operation, a constant speed of say 1-2 RPM is preferable to maintain the quality of the concrete in the mixer drum. Because the motor is driving both the vehicle and the drum, fuel consumption used to drive the mixer drum is high, the generation of noise is high and the power transmitted to the vehicle is reduced thus consuming more fuel. Additionally, because the drum is driven at speeds higher than necessary, the wear on components is greater than it need be.

It is an object of present invention to provide a drive system of the type referred to in which one or more 6f the aforementioned disadvantages is reduced or obviated.

According to the present invention, a drive system of the type referred to comprises an electromechanical control device for controlling the displacement of the pump, an electronic circuit arrangement and sensor means for providing a signal proportional to the speed of rotation of the drum to the circuit arrangement, the device being operable by the circuit arrangement to maintain the speed of rotation of the drum at a pre-set speed.

Preferably, the device is switchable between the circuit arrangement and an electrical output from the second lever whereby the device is operable either by the circuit arrangement or by the second lever.

A drive system of the type referred to will now be described to illustrate the invention by way of example only with reference to the accompanying drawing which diagrammatically shows the drive system.

The drive system 10 is mounted on a vehicle chassis (not shown) along with a concrete mixer drum 1 2 in known manner. The drive system 10 has a motor 14 in the form of the vehicle's diesel engine; a variabledisplacement hydraulic pump 1 6 which is supplied with hydraulic fluid from a reservoir (not shown) and which is driven by the motor 14; a hydraulic turbine 1 8 which receives high pressure hydraulic fluid from the pump 1 6 through high pressure lines 20; and a transmission 22 which is driven by the turbine 18 and which drives the drum 12.

The motor 1 4 has an injector pump 24 which is operated either by the foot pedal 26 of known type in the cab of the vehicle or by a lever 28 connected to the unit 24 by a Bowden cable.

The hydraulic pump 1 6 has an electromechanical device 30 which controls the pilot valve controlling the displacement of the pump 1 6. Typically the device 30 is a MCV 1 04A type device available from Sundstrand Mobile Controls, Sundstrand Corp., Minnesota, USA. By means of a selector switch unit 32, the device 30 is operable either by the levers 34, 36 located in the cab of the vehicle and at the rear of the vehicle, respectively, or by an electronic circuit arrangement 38.

The levers 34, 36 are electrical controls typically of the type designated MCHXXX available from the aforementioned Sundstrand. Movement of either lever 34, 36 provides an electrical control signal to operate the device 30 to determine the displacement of the pump 16.

The circuit arrangement 38 provides an electrical control signal to operate the device to determine the displacement of the pump 1 6 thereby controlling the speed of the drum at a selected one of two pre-set rates, for example 1 or 10 RPM, depending on the particular operation involved. The pre-set rates can be altered by the operator to suit the particular application for which the drum is to be used. The circuit arrangement 38 receives a feedback signal from a drum speed sensor (not shown) via line 40. Typically, the circuit arrangement 38 is of a type known as a P1 Controller (PID-Regulator Type MCE) available from Sauer Getriebe, Germany.

The sensor is preferably used to provide a visual readout of drum speed at 42 for the operator's guidance.

In operation, the operator uses the switch 32 to select control of the displacement of the pump 1 6 by means of the circuit arrangement 38 and selects the 10 RPM setting on the arrangement 38. The operator sets the speed of the motor 14 using the lever 28 to a rate sufficient to rotate the drum (when loaded) at 10 RPM and switches the circuit arrangement 38 on. Thereafter, during the loading operation, automatically adjusts the displacement of the pump 1 6 to maintain the speed of rotation of the drum 1 2 at the pre-set value.

Once loading has been completed, the operator then selects the 1 RPM setting on the circuit arrangement 38 and moves the lever 28 back to its zero setting, the idle speed of the motor 14 providing sufficient power to drive the drum at 1 RPM. The circuit arrangement 38 then automatically adjusts the displacement of the pump 1 6 to maintain the speed of the drum 1 2 at the pre-set value even when the vehicle travels from the loading installation to the site at which the material is to be used.

In order to discharge material, the operator uses the switch 32 to select control of the displacement of the pump 1 6 by means of the levers 34, 36. Then, using either the foot pedal 26 and the lever 34 or the levers 28 and 36 to control the speed of rotation of the drum 2, the operator can discharge material from the drum 1 2.

It will be appreciated that the maintenance of the speed of rotation at the pre-set values during loading and agitating operations will reduce component wear, reduce fuel consumption (the motor 14 does not to have to be accelerated to accommodate changing loads or to be used to drive the drum faster than required) and reduce noise. Additionally, when travelling a greater proportion of the motor's power will be available to propel the vehicle thus further reducing use of fuel and generation of noise.

The arrangement shown in the drawing is schematic only and is not intended to be definitive. For example, there are several ways of connecting the motor 14 to the pump 16.

In an alternative arrangement (not shown), the motor 14 is not the drive motor of the vehicle but is a separate motor mounted on the chassis of the vehicle. In another modification, the levers 34, 36, instead of being electrical control handlers, could be conventional levers connected to Bowden cables which either terminate in transducers or mechanically adjust the displacement of the pump, the device 30 being inoperative. Although in the drawing the sensor is indicated as being in the transmission 22, it will be apparent that a signal proportional to the speed of rotation of the drum 1 2 could be readily derived from the turbine 1 8. Although in the drawing the turbine 18 is shown as being externally mounted to the transmission 22, it may be mounted internally thereof as a fully-integrated hydraulic-mechanical device whilst not changing the operation of the drive system.

Claims

1. A drive system of the type referred to comprising an electromechanical control device for controlling the displacement of the pump, an electronic circuit arrangement and sensor means for providing a signal proportional to the speed of rotation of the drum to the circuit arrangement, the device being operable by the circuit arrangement to maintain the speed of rotation of the drum at a pre-set speed.

2. A drive system according to claim 1, in which the device is switchable between the circuit arrangement and an electrical output from the second lever, whereby the device is operable either by the circuit arrangement or by the second lever.

3. A drive system according to claim 1 substantially as hereinbefore described with reference to the accompanying drawing.

4. A vehicle having a mixer drum mounted thereon comprising a drum drive system as claimed in any one of the preceding claims.