GB1596361A

GB1596361A - Drive assemblies

Info

Publication number: GB1596361A
Application number: GB1841378A
Authority: GB
Original assignee: EFFEPI SNC
Current assignee: EFFEPI SNC
Priority date: 1978-05-09
Filing date: 1978-05-09
Publication date: 1981-08-26

Description

(54) IMPROVEMENTS IN AND RELATING TO DRIVE ASSEMBLIES (71) We, EFFEPI S.N.C. an Italian Body Corporate of Via del Parco 23, Bologna, Italy. 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 statement: The present invention relates to drive assemblies and has particular but not ex clusive application in an actuator system for the rapid opening and closing of ball valves and the like.

Ball valves or throttle valves as they are sometimes called are frequently employed in fluid circuits where they are operated by the reciprocating piston rod of a double acting pneumatic piston. The rectilinear motion of the piston has to be converted into a rotary motion to operate the control spindle of the ball valve and rack and pinion assemblies are frequently employed for this purpose.

According to the present invention, a drive assembly for converting rectilinear motion into rotary motion comprises a hollow cylindrical cam part having in its curved surface a slot which provides a cam surface of generally helical configuration without any axially disposed end portions and a cam-engaging part projecting through the slot from within the hollow core region of the cylindrical cam part to co-operate with a guide surface provided in an outer housing to lock the cam-engaging part against rotary motion whereby relative rec tilinear motion between the cam part and the cam-engaging part will give rise to relative rotary motion Conveniently, the guide surface is pro vided by a longitudinal slot formed in the curved surface of the cylindrical housing and lying parallel to the direction of recti linear motion. In this case the cam-engaging part may, if desired, project externally of the housing to allow manual operation of the assembly, e.g. in the event that the pneumatic piston malfunctions.

As already indicated above, the drive assembly of the present invention provides an attractive alternative to the rack and pinion assemblies currently employed in some valve actuator systems. As compared with these known systems actuator systems employing the drive asembly of the present invention will usually be smaller and have shorter response times.

In all the variations of the present invention described above, only one cam surface has been referred to. Generally speaking however the drive assembly will have a longitudinal axis of symmetry and it is then preferable to have two such cam surfaces arranged opposite to one another about this axis.

Thus in a preferred embodiment of the invention for use in a valve actuator system, the assembly comprises a hollow cylindrical cam part having in its curved surface, two opposed helical slots lacking any axially disposed end portions, a hollow cylindrical housing having two opposed longitudinal slots lying parallel to the axis of symmetry of the assembly, a cam-engaging part extending from within the hollow core region of the cylindrical cam part through the helical slots in the cam part and into or through the longitudinal slots in the housing, means for connecting the cam-engaging part with the piston rod of a pneumatically operated piston and cylinder device, means for connecting the housing of the drive assembly with the housing of the piston and cylinder device and the housing of a ball valve or the like, and means for connecting the cam part with the control spindle of the ball valve or the like.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a perspective view of a valve actuator system including a drive assembly embodying the present invention, and Figure 2 is an exploded view of the system shown in Figure 1.

Thus referring to the drawings, a drive assembly according to the present invention comprises a hollow cylindrical cam part 18 having two opposed helical slots 16 machined in its curved surface (Figure 2).

At its lower end, the part 18 is partially closed by a base plate having a central aperture 14 of hexagonal cross-section.

The cam part 18 is constrained within a cylindrical housing 2 having two opposed slots 17 machined in it to lie parallel to the axis of symmetry of the assembly. At its upper end 19 the housing 2 is internally threaded so that it can be screwed onto a corresponding portion 20 of a pneumatic piston and cylinder device 1. At its lower end, the housing 2 is provided with three grub screws 18 (of which only two are visible in the drawing) allowing it to be secured to a shoulder portion of a ball valve 3 which in turn forms part of a hydraulic circuit (not shown).

The operating spindle 13 of the valve carries a nut 15 which is accepted by the aperture 14 in the cam part base plate.

Lock nut 11 is a self-locking nut which is screwed down onto that part of spindle 13 projecting above the base plate to lock the cam part 18 onto the valve spindle.

The assembly is completed by the camengaging part which takes the form of a transverse pin having a central body portion 7 screwed onto the threaded end of the piston rod 5. From body portion 7 extend two arm portions each composed of a series of sliding rotatable sleeve lengths 8 separated by spring washers 9. Through these, and a corresponding aperture in the body portion 7, is passed an internally threaded cylindrical section 6. The constituent parts of the arm portions are finally locked together by threaded stud members 10 which are screwed into place through the slots 17 when the remainder of the cam-engaging part has been assembled within the housing 2. Two knob portions at the outer ends of stud members 10 prevent the sleeve lengths 8 and washers 9 from sliding off the cylindrical section 6 and facilitate manual operation of the assembly.

Assuming the initial siuation to be that illustrated in Figure 1, with the valve 3 half open say, the assembly may for example be operated by introducing compressed air through the lower inlet 4 of device 1 to drive the piston upwards and with it the cam-engaging part 7-10. As the cam engaging part is locked against rotation by the slots 17, the upwards motion of the cam-engaging part is accommodated by a corresponding clockwise rotation of the cam part 18 as the cam-engaging part rides up the helical slots 16 in the cam part. This rotation of cam part 18 will of course produce a corresponding rotation of the valve spindle 13 to close or "choke" the valve 3.

Compressed air introduced into the device 1 through the top inlet (4') can of course be used to rotate the valve spindle in the opposite sense to open the valve again, the lowermost position of the camengaging part conveniently corresponding to the fully open position of the valve.

If desired the dou'ble-acting cylinder device 1 can be replaced by one using a single-acting elastic-return cylinder.

WHAT WE CLAIM IS:- 1. A drive assembly for converting rectilinear motion into rotary motion comprising a hollow cylindrical cam part having in its curved surface a slot which provides a cam surface of generally helical configuration without any axially disposed end portions and a cam-engaging part projecting through the slot from within the hollow core region of the cylindrical cam part to co-operate with a guide surface provided in an outer housing to lock the camengaging part against rotary motion whereby relative rectilinear motion between the cam part and the cam-engaging part will give rise to relative rotary motion.

2. An assembly as claimed in Claim 1 in which the guide surface is provided by a longitudinal slot formed in the curved surface of the cylindrical housing and lying parallel to the direction of rectilinear motion.

3. An assembly as claimed in Claim 2 in which the cam-engaging part projects externally of the housing to allow manual operation of the assembly.

4. An assembly as claimed in any preceding Claim in which the assembly is symmetrical about a longitudinal axis, and the cam surface is one of two such surfaces arranged opposite to one another about this axis.

5. A device for controlling fluid flow comprising a drive assembly according to any preceding Claim and a valve adapted to be closed or opened by rotary motion of a control member of the valve, the control member of the valve being coupled to a part of the drive assembly which is arranged to provide a rotary output motion.

6. A device according to Claim 5 including a double acting pneumatic piston coupled to a part of the drive assembly adapted to receive a linear input motion.

7. A device according to Claim 5 or 6 in which the valve comprises a ball or throttle valve.

8. A drive assembly symmetrical about a longitudinal axis and comprising a hollow cylindrical cam part having, in its curved surface, two opposed helical slots lacking any axially disposed end portions, a hollow cylindrical housing having two opposed longitudinal slots lying parallel to the axis of symmetry of the assembly, a cam engaging part extending from within the hollow core region of the cylindrical cam

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. At its lower end, the part 18 is partially closed by a base plate having a central aperture 14 of hexagonal cross-section. The cam part 18 is constrained within a cylindrical housing 2 having two opposed slots 17 machined in it to lie parallel to the axis of symmetry of the assembly. At its upper end 19 the housing 2 is internally threaded so that it can be screwed onto a corresponding portion 20 of a pneumatic piston and cylinder device 1. At its lower end, the housing 2 is provided with three grub screws 18 (of which only two are visible in the drawing) allowing it to be secured to a shoulder portion of a ball valve 3 which in turn forms part of a hydraulic circuit (not shown). The operating spindle 13 of the valve carries a nut 15 which is accepted by the aperture 14 in the cam part base plate. Lock nut 11 is a self-locking nut which is screwed down onto that part of spindle 13 projecting above the base plate to lock the cam part 18 onto the valve spindle. The assembly is completed by the camengaging part which takes the form of a transverse pin having a central body portion 7 screwed onto the threaded end of the piston rod 5. From body portion 7 extend two arm portions each composed of a series of sliding rotatable sleeve lengths 8 separated by spring washers 9. Through these, and a corresponding aperture in the body portion 7, is passed an internally threaded cylindrical section 6. The constituent parts of the arm portions are finally locked together by threaded stud members 10 which are screwed into place through the slots 17 when the remainder of the cam-engaging part has been assembled within the housing 2. Two knob portions at the outer ends of stud members 10 prevent the sleeve lengths 8 and washers 9 from sliding off the cylindrical section 6 and facilitate manual operation of the assembly. Assuming the initial siuation to be that illustrated in Figure 1, with the valve 3 half open say, the assembly may for example be operated by introducing compressed air through the lower inlet 4 of device 1 to drive the piston upwards and with it the cam-engaging part 7-10. As the cam engaging part is locked against rotation by the slots 17, the upwards motion of the cam-engaging part is accommodated by a corresponding clockwise rotation of the cam part 18 as the cam-engaging part rides up the helical slots 16 in the cam part. This rotation of cam part 18 will of course produce a corresponding rotation of the valve spindle 13 to close or "choke" the valve 3. Compressed air introduced into the device 1 through the top inlet (4') can of course be used to rotate the valve spindle in the opposite sense to open the valve again, the lowermost position of the camengaging part conveniently corresponding to the fully open position of the valve. If desired the dou'ble-acting cylinder device 1 can be replaced by one using a single-acting elastic-return cylinder. WHAT WE CLAIM IS:-

1. A drive assembly for converting rectilinear motion into rotary motion comprising a hollow cylindrical cam part having in its curved surface a slot which provides a cam surface of generally helical configuration without any axially disposed end portions and a cam-engaging part projecting through the slot from within the hollow core region of the cylindrical cam part to co-operate with a guide surface provided in an outer housing to lock the camengaging part against rotary motion whereby relative rectilinear motion between the cam part and the cam-engaging part will give rise to relative rotary motion.

part through the helical slots in the cam part and into or through the longitudinal slots in the housing, means for connecting the cam engaging part with the piston rod of a pneumatically operated piston and cylinder device, means for connecting the housing of the drive assembly with the housing of the piston and cylinder device and the housing of a ball valve or the like, and means for connecting the cam part with the control spindle of the ball valve or the like.

9. A drive assembly substantially as herein"oefore described with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings.

10. A device for controlling fluid flow substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings.