GB1594486A - Swing apparatus - Google Patents

Description

(54) SWING APPARATUS (71) We, MASSEY-FERGUSON INC., 12601 Southfield Road, Detroit, Michigan 48223, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following staeement: - This invention relates to swing apparatus and particularly, though not exclusively to such apparatus for controlling the side to side swinging movement of a backhoe digger boom. The invention is an improvement in or modification of the apparatus described and claimed in our British Patent No.

1,546,252.

In the swing apparatus described in the above referred to patent application a pair ef linear hydraulic cylinders were used as the power means to swing the boom and various flow paths were available in the fluid piping system for fluid to return frown these cylinders.

One of the flow paths was across a directional valve used to control the direction of swing of the boom. This necessitawd the direstionail valve being a two-way valve so that the returning fluid could be directed to a sump. A second flow path was through a cross line extending between supply and return lines of the power means, this cross line being also connected to sump. A third flow path was provided in that fluid leaving part of the power means was able to flow to another part of the power means via the supply line thus assisting in preventing cavitation in the system.

The third flow path described above is the preferred path whenever fluid was re quired by said another part of the power means but the piping system described in the parent application allowed a random choice of flow path to be made. Further, the first path required the directional valve to be a two way valve. As indicated above it is an object of the present invention to provide an improved form of swing apparatus which overcomes the above shortcomings of the apparatus described in the parent patent.

According to one aspect of the present invention there is provided swing apparatus as claimed in claim 1 of British Patent No.

1,546,252 wherein a fluid connection is provided between said s.econd metering valve means and said one line, a fist check valve being provided in said connection to pernait flow from said other line to said one line but preventing flow in the revense direction, a second check valve being provided in said one line at a location between the junction of said connection and said one line and the source, said second check valve permitting flow to said power means through said one line but preventing flow from said power means through said one line on the source side of said junction, and return flow paths being provided to a sump for both said one and other lines at locations on the power means side of said junction.

As will be appreciated, by preventing flow from the power means through that part of said one line on the source side of the check valve, the first return path referred to above is eliminated and it is possible to use a one way directional valve to supply pressurised fluid from the source to either line alternatively to control the direction of swing of said member. This is an improvement over the apparatus described in the parent application in which, as described above, a twoway directional valve was necessary.

The present invention also provides swing apparatus as claimed in claim 13 of British Patent No. 1,546,252 wherein a respective fluid connection is provided between said second metering valve means and slaid one line of each respective pair of lines, a first check valve being provided in each respective connection to permit flow from said other line to said one line d each respective pair but prevent flow in the reverse direction, a second check valve being provided in said one line of each respective pair at a location between the junction of said respective connection and said respective one line and the source, each respective second check valve permitting flow to said respective cylinder through said respective one line but preventing flow from said respective cylinder through said respective one line on the source od said respective junction, and return flow paths being provided to a sump for both lines of each respective pair at locations on the cylin der side of each respective junction.

Preferably each return flow path includes a portion ob said respective fluid connection, the arrangement being such that fluid entering each respective connection flows to said respective one line in preference to said sump.

The (or each respective) second metering vaLve means may be provided with a pilot line connected with said one line (or said line of the respective pair) at a location between said second check valve (or said respective second check valve) and the source.

One embodiment od the invention as applied to a backhoe boom swing apparatus will now be described, by way of example only, with reference to the accompanying drawing.

Referring to the drawing the hydraulic system indicated collectively by reference numeral 15 is illustrated with common reference numerals identifying common components to those shown in Figure 3 of the parent application.

The geometry of the power means 6, 6' and swing bnacket 2 of Figure 1 of the parent application is the same for the present application and, therefore, Figure 1 of the parent application is not repeated herein. The parent application fully describes the purpose and function od the above geometry and such des cription will not therefore be repeated here.

Returning to the drawing of the present application the supportive components to the hydraulic system disclosed, such as the pump 16 and sump 19 etc., are also as disclosed in the parent application. One exception has already been noted and that is that the directional valve 18 is now a single acting valve.

Turning to the circuit disclosed, main line 20 is connected via a check valve 22 with one end of a supply line 23, the other end of line 23 being connected with a head end line 24 to the head end of actuator 6. Note that check valve 22 has been relocated over the position in the supply line in Figure 3 of the parent application which change will be taken up below. The rod end of actuator 6 is connected with a rod end line 26. Sinai- larly, main line 20' is connected via a check valve 22' with a supply line 23' and a head end line 24' to the head end of actuator 6', the rod end of actuator 6' being connected with a rod end line 26'. Check valve 22' has been relocated in the same manner as check valve 22.

Actuation of the directional valve 18 to the right or left from the neutral position shown in the drawing energizes the hydraulic årcuit 15 to supply fluid either to the head end of actuator 6 or to the head end of actuator 6'. When valve 18 is actuated to the right, fluid is supplied to the head end of actuator 6 and to the rod end of actuator 6' resulting in clockwise swinging movement of the swing bracket 2 (illustrated only by its axis).Conversely, actuation of valve 18 to the left causes fluid to be supplied from pump 16 to the head end of actuator 6' and rod end of actuator 6 which results in counterclockwise swinging movement of the swing bracket 2.

When fluid pressure is supplied to the head end of one of the actuators 6 or 6', the actuator is urged to extend by the head end fluid pressure. Conversely, when fluid pressure is supplied to the nod end of one of the actuators 6 or 6', the rod end fluid pressure urges the actuators to retract.However, when one of the actuators is in an overcentre position with respect to the axis of support member 4 so that its line od force is on the same side of support member 4 as that of the other actuator, the swing bracket 2 will prevent movement of the actuator in the direction urged by the fluid pressure acting on the actuator until the actuator moves from the overcentre position to the opposite side of the swing axis, i.e. the axis of the swing bracket support member 4.

A anoss line 30, 30' extends between lines 23 and 23', and lines 26 and 26' are aonnected with the cross line 30, 30' through drain lines 27 and 27'. Lines 24 and 24' are connected with the cross line 30, 30' through head end drain line 28. Line 26 is connected with lines 20' and 24' through line 23' by interconnecting line 32' bypassing line 27' and controlled by a check valve 34'.

Similarly, line 26' is connected with lines 20 and 24 though line 23 by interconnecting line 32 controlled by a check valve 34 and bypassing line 27. A check valve 36 is located in line 30 between its connection with line 23 and its connection with line 27. Similarly, a check valve 36' is located in line 30' between its connection with line 27' and its connection with line 23'.

The flow to the head end of actuator 6 through line 24 is controlled by a normally open pressure reducing mitering valve 38 which limits the pressure in line 24 to a predetermined maximum by - closing to shut off flow to line 24 from line 23 when the predetermined maximum pressure exists in line 24. The pressure reducing mitering valve 38 is controlled by a pilot pressure in a pilot line 40 connected with line 24 so as to sense the pressure at the head end of aotwator 6.

When line 20 is connected with the supply line 17, the pressure reducing metering valve 38 begins to close off the flow line 24 when the pressure approaches a predetermined maximum, and shuts off the flow to line 24 when the pressure, as sensed through the pilot line 40, exceeds the predetermined maxi mum pressure. A similar pressure reducing metering valve 38' controls the pressure of hydraulic fluid to the head end of actuator 6' through line 24'.

Line 26 is controlled by a normally closed rod end metering valve 42'. Valve 42' is connected through a pilot line 44' with line 26, and through a pilot line 46' witch line 20. If the pressure in the pilot lines 44' or 46' reaches a predetermined value to OVR- acme the spring force biasing valve 42' to its closed position, valve 42' will begin to open and permit flow from the rod end of astulator 6 through liners 26 and 27' to line 30', 30.

Line 28 is controlled by the pressure reducing metering valve 38 which has a detering as well as a pressure reducing function and has the pilot line 40 also connected with the detering function. When a predetermined pressure is reached in plot line 40 the valve 38 overcomes the spring force biasing it alose to its port to line 28 and begins to open permitting flow through line 28 from valve 38 to line 60 from line 24.

Flow through valve 38 from line 23 to line 24 occurs at a lower pressure than when flow is being forced from the head end of actuator 6 into line 28 from line 24. When flow is from line 24 to line 28 the port of valve 38 connected to line 23 is blocked off.

Similarly metering valve 42 and pressure reducing metering valve 38' control line 26' and line 28 in conjunction with line 24', respectively.

It will be understood by those skilled in the art that each of the valves 38, 38' could be replaced by two separate valves, one valve performing the pressure reducing function and the other valve performing the mitering function.

A no'real operating cycle for the hydraulic system 15 when swinging the swing mechanism is described in the parent application and will not therefore be repeated herein.

Returning to the relocation of the check valve 22 land 22', it was found that locating the valves 22 'and 22' below the cross line 30, 30' rather than between the cross line 30, 30' and interconnecting lines 32, 32' re sulked in 'preventing flow from line 30, 30' passing across checks 36, 36' into lines 20, 20' and across the directional valve 18 which has therefore become a single acting or one way valve.

Further, under conditions where the metering valve 42 or 42' is functioning and fluid passing through 4ine 27 or 27' to cross line 30, 30' it is advantageous to direct whatever portion of Ithe flow rmay be needed to the head end of the actuator 6 or 6' in order to assist in preventing cavitation.

Under these drcumstances it is preferred to have the fluid travel from cross line 30, 30' to supply 'l'ine 23 or 23' across normally open pressure reducing metering valve 38, or 38' through line 24 or 24' into the helad end of the appropffate actuator 6 or 6'.

It will be recognised that there is an alternative flow path through line 30, 30' to sump 19 which is necessary to return the balance of the fluid to sump 19. A preference to have fluid flow to the head end of actuator 6 or 6' is maintained by sizing the line to sump 19 smaller than .the line 23 or 23'. The above preference in flow is enhanced by the increase in flow resulting from ehle check valves 22 or 22' preventing flow across the directional valve 18.

The opposite hand function occurs for detering valve 42' and line 27'.

The system of this invention provides improved control for most conditions where the actuators 6 and 6' would cavitate in the absence of the system providing fluid to the actuators 6 and 6'.

Another advantage is the system permits the use of a single acting directional valve over the double acting one required in the parent patent.

While the invention has been described specifically in connection with backhoe swing apparatus, it is apparent that the invention is suitable for other uses, and particularly with other apparatus having a swinging boom.

Therefore, terms and phrases, such as "backhoe" and "backhoe swing apparatus" as used herein, mean any such apparatus having a boom or Ithe like, that is normally hydrau locally operated.

WHAT WE CLAIM IS: 1. Swing apparatus as claimed in claim 1 of British Patent No. 1,546,252 wherein a fluid connection is provided between said second metering valve means and said one line, a first check valve being provided in said connection to permit flow from said other line to said one line but preventing flow in the reverse direction, a second check valve being provided in said one line at a location between the junction of said connection and said one line and the source, said second check valve permitting flow to said power means through said one line be p.reven.ting flow from said power means through said one line on the source side of said junction, and return flow paths being provided to a sump for beth said one and other lines at locations on the power means side of said junction.

2. Swing apparatus as claimed in claim 13 of British Patent No. 1,546,252 wherein a respective fluid connection is provided between said second metering valve means and said one 'line of each respective pair of lines, a finst check valve being provided in each respective 'connection to permit flow from said other line to said one line of each respective p.air but prevent flow in the reverse direction,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. mum pressure. A similar pressure reducing metering valve 38' controls the pressure of hydraulic fluid to the head end of actuator 6' through line 24'. Line 26 is controlled by a normally closed rod end metering valve 42'. Valve 42' is connected through a pilot line 44' with line 26, and through a pilot line 46' witch line 20. If the pressure in the pilot lines 44' or 46' reaches a predetermined value to OVR- acme the spring force biasing valve 42' to its closed position, valve 42' will begin to open and permit flow from the rod end of astulator 6 through liners 26 and 27' to line 30', 30. Line 28 is controlled by the pressure reducing metering valve 38 which has a detering as well as a pressure reducing function and has the pilot line 40 also connected with the detering function. When a predetermined pressure is reached in plot line 40 the valve 38 overcomes the spring force biasing it alose to its port to line 28 and begins to open permitting flow through line 28 from valve 38 to line 60 from line 24. Flow through valve 38 from line 23 to line 24 occurs at a lower pressure than when flow is being forced from the head end of actuator 6 into line 28 from line 24. When flow is from line 24 to line 28 the port of valve 38 connected to line 23 is blocked off. Similarly metering valve 42 and pressure reducing metering valve 38' control line 26' and line 28 in conjunction with line 24', respectively. It will be understood by those skilled in the art that each of the valves 38, 38' could be replaced by two separate valves, one valve performing the pressure reducing function and the other valve performing the mitering function. A no'real operating cycle for the hydraulic system 15 when swinging the swing mechanism is described in the parent application and will not therefore be repeated herein. Returning to the relocation of the check valve 22 land 22', it was found that locating the valves 22 'and 22' below the cross line 30, 30' rather than between the cross line 30, 30' and interconnecting lines 32, 32' re sulked in 'preventing flow from line 30, 30' passing across checks 36, 36' into lines 20, 20' and across the directional valve 18 which has therefore become a single acting or one way valve. Further, under conditions where the metering valve 42 or 42' is functioning and fluid passing through 4ine 27 or 27' to cross line 30, 30' it is advantageous to direct whatever portion of Ithe flow rmay be needed to the head end of the actuator 6 or 6' in order to assist in preventing cavitation. Under these drcumstances it is preferred to have the fluid travel from cross line 30, 30' to supply 'l'ine 23 or 23' across normally open pressure reducing metering valve 38, or 38' through line 24 or 24' into the helad end of the appropffate actuator 6 or 6'. It will be recognised that there is an alternative flow path through line 30, 30' to sump 19 which is necessary to return the balance of the fluid to sump 19. A preference to have fluid flow to the head end of actuator 6 or 6' is maintained by sizing the line to sump 19 smaller than .the line 23 or 23'. The above preference in flow is enhanced by the increase in flow resulting from ehle check valves 22 or 22' preventing flow across the directional valve 18. The opposite hand function occurs for detering valve 42' and line 27'. The system of this invention provides improved control for most conditions where the actuators 6 and 6' would cavitate in the absence of the system providing fluid to the actuators 6 and 6'. Another advantage is the system permits the use of a single acting directional valve over the double acting one required in the parent patent. While the invention has been described specifically in connection with backhoe swing apparatus, it is apparent that the invention is suitable for other uses, and particularly with other apparatus having a swinging boom. Therefore, terms and phrases, such as "backhoe" and "backhoe swing apparatus" as used herein, mean any such apparatus having a boom or Ithe like, that is normally hydrau locally operated. WHAT WE CLAIM IS:

1. Swing apparatus as claimed in claim 1 of British Patent No. 1,546,252 wherein a fluid connection is provided between said second metering valve means and said one line, a first check valve being provided in said connection to permit flow from said other line to said one line but preventing flow in the reverse direction, a second check valve being provided in said one line at a location between the junction of said connection and said one line and the source, said second check valve permitting flow to said power means through said one line be p.reven.ting flow from said power means through said one line on the source side of said junction, and return flow paths being provided to a sump for beth said one and other lines at locations on the power means side of said junction.

2. Swing apparatus as claimed in claim 13 of British Patent No. 1,546,252 wherein a respective fluid connection is provided between said second metering valve means and said one 'line of each respective pair of lines, a finst check valve being provided in each respective 'connection to permit flow from said other line to said one line of each respective p.air but prevent flow in the reverse direction,

a second check valve being provided in said one line of each respective pair at a location between the junction of said respective con nection and said respective one line and the source, each respective second check valve permitting flow to said respective cylinder through said respective one line but preventing flow from said respective cylinder through said respective one line on the source side of said respective junction, and return flow paths being provided to a sump for both lines of each respective pair at locations on the cylinder side of each respective junction.

3. Swing apparatus according to claim 1 or claim 2 wherein each return flow path includes a portion of said respective fluid connection, the arrangement being such that fluid entering each respective connection flows to said respective one line in preference to said sufnp.

4. Swing apparatus according to any one of alaiints 1 to 3 wherein the (or each res- pe.ative) second metering valve means is pro vided with a pilot line connected with said one line (or said one line of the respective pair) at a location between said second check valve (or said respective second check valve) and the source.

5. Swing apparatus constructed and arranged substantially as hereinbefore described with reference to and as shown in the eccom- paning drawing.