GB2166835A

GB2166835A - Movement converting device

Info

Publication number: GB2166835A
Application number: GB08528081A
Authority: GB
Inventors: Francis Ronald Crowfoot
Original assignee: British Aerospace PLC
Current assignee: BAE Systems PLC
Priority date: 1984-11-14
Filing date: 1985-11-14
Publication date: 1986-05-14
Also published as: GB2166835B; GB8528081D0

Abstract

A movement converting device includes a support member 10 having an internally threaded bore 12 which receives a threaded shaft 15. The periphery of the shaft 15 is provided with a plurality of groves 17 to define a plurality of longitudinal extending teeth. A drive wheel 14 is rotatably mounted on the support member 10 and meshes with the longitudinal groves. Rotation of drive wheel 14 effects longitudinal movement of shaft 15. <IMAGE>

Description

SPECIFICATION Movement converting device This invention relates to movement converting devices for converting rotary motion into linear motion.

In a known example of such a device, commonly known as a screwjack, a threaded shaft is rotatably supported at both ends by means of a fixed bracket. Rotational drive is supplied to one end of the shaft and a carriage is threadedly engaged with the shaft and prevented from rotation with respect to the bracket. Rotation of the shaft is converted by this arrangement into longitudinal movement of the carriage.

According to this invention, there is provided a movement converting device which includes a support member including a threaded bore, an elongate shaft having a threaded portion for threadedly engaging said bore, said threaded portion being provided with a plurality of elongate grooves spaced around the periphery thereof, and drive means mounted on said support member for drivably engaging said grooves whereby operation of said drive means effects rotation of the shaft relative to said support member, thereby to effect longitudinal movement of the shaft with respect to said support member.

By this arrangement, the drive input is applied directly between the shaft and the support member to effect relative longitudinal thereby providing a compact arrangement.

Said drive means preferably includes a toothed drive wheel rotatably mounted on said support member. Preferably, the drive means includes a motor mounted on the support member.

In one embodiment the support member is of hollow cylindrical form including at one end an end wall having means for attachment to a further structural member.

By way of example only three specific embodiments of this invention will now be described in detail, reference being made to the accompany drawings in which Figure 1 is a side sectional view of a first embodiment of this invention, Figure 2 is a cross sectional view of the embodiment of Fig. 1 taken on lines ll-ll; Figure 3 is a side sectional view of an air intake assembly incorporating a second embodiment of this invention; and Figure 4 is a side sectional view of a third embodiment of this invention.

Referring initially to Figs. 1 and 2 the embodiment illustrated comprises a support housing 10 including a generally cylindrical portion 11 having a threaded bore 12 and a pair of opposed flanges 13 for mounting the housing on a fixed structure. An input drive gear wheel 14 is journalled on the housing, and has teeth which mesh with the output drive shaft 15 as to be described below.

The output drive shaft 15 includes a threaded portion 15 for threaded engagement with bore 12, the portion 16 being provided with a plurality of longitudinally extending grooves 17 spaced around its periphery to define a plurality of longitudinally extending teeth which mesh with the teeth of the drive wheel. The depth of the screw thread is typically one half of the depth of the longitudinal grooves.

In use, rotation of the input gear wheel 14 causes relative rotation between the output drive shaft 15 and the housing 10 and thereby effects longitudinal movement of the output shaft relative to the housing.

Referring to Fig. 3 there is illustrated an arrangement located in the nose region of a flight vehicle operable for controlling the flow of ram air into a duct. The arrangement includes an outer casing 20 having an inner wall 21 defining a duct, and a generally conical portion 22 mounted for movement with respect to said outer casing between a position in which they define a substantially continuous exterior surface (as illustrated in full lines) and a position in which the conical portion 22 is withdrawn to define an annular intake for ram air (as illustrated in chain dotted lines). Movement of the conical portion relative to the outer casing is effected by means of a screw jack 23 of similar form to the embodiment of Fig. 1 and similar items will be given similar references.

The screw jack 23 comprises a housing 10 having one end secured to a structural member of the outer casing 20 and supporting an output shaft 15 to the outer end of which is secured the conical portion 22 by means of radial spokes 24 and thrust washers 25. The output shaft is provided with a threaded portion 16 having longitudinal grooves 17 to define a plurality of teeth. The threaded portion 16 is received in threaded bore 12 of the housing 10 and the teeth of the shaft engage the teeth of an idler gear wheel 26 rotatably mounted in the housing. The idler wheel 26 meshes with input gear wheel 14 which is driven by means of a drive motor 27 secured to the housing.

Referring now to Fig. 4 the third embodiment illustrated is similar to that illustrated in Fig. 2 except that the housing is provided with an attachment lug 30 located coaxially with respect to the drive shaft 15. The threaded portion of the drive shaft extends only part-way along the length thereof and pivotally supports a U-shaped coupling member 31 by means of thrust washers 25.

1. A movement converting device which includes a support member including threaded bore, an elongate shaft having a threaded portion for threadedly engaging said bore, said

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Movement converting device This invention relates to movement converting devices for converting rotary motion into linear motion. In a known example of such a device, commonly known as a screwjack, a threaded shaft is rotatably supported at both ends by means of a fixed bracket. Rotational drive is supplied to one end of the shaft and a carriage is threadedly engaged with the shaft and prevented from rotation with respect to the bracket. Rotation of the shaft is converted by this arrangement into longitudinal movement of the carriage. According to this invention, there is provided a movement converting device which includes a support member including a threaded bore, an elongate shaft having a threaded portion for threadedly engaging said bore, said threaded portion being provided with a plurality of elongate grooves spaced around the periphery thereof, and drive means mounted on said support member for drivably engaging said grooves whereby operation of said drive means effects rotation of the shaft relative to said support member, thereby to effect longitudinal movement of the shaft with respect to said support member. By this arrangement, the drive input is applied directly between the shaft and the support member to effect relative longitudinal thereby providing a compact arrangement. Said drive means preferably includes a toothed drive wheel rotatably mounted on said support member. Preferably, the drive means includes a motor mounted on the support member. In one embodiment the support member is of hollow cylindrical form including at one end an end wall having means for attachment to a further structural member. By way of example only three specific embodiments of this invention will now be described in detail, reference being made to the accompany drawings in which Figure 1 is a side sectional view of a first embodiment of this invention, Figure 2 is a cross sectional view of the embodiment of Fig. 1 taken on lines ll-ll; Figure 3 is a side sectional view of an air intake assembly incorporating a second embodiment of this invention; and Figure 4 is a side sectional view of a third embodiment of this invention. Referring initially to Figs. 1 and 2 the embodiment illustrated comprises a support housing 10 including a generally cylindrical portion 11 having a threaded bore 12 and a pair of opposed flanges 13 for mounting the housing on a fixed structure. An input drive gear wheel 14 is journalled on the housing, and has teeth which mesh with the output drive shaft 15 as to be described below. The output drive shaft 15 includes a threaded portion 15 for threaded engagement with bore 12, the portion 16 being provided with a plurality of longitudinally extending grooves 17 spaced around its periphery to define a plurality of longitudinally extending teeth which mesh with the teeth of the drive wheel. The depth of the screw thread is typically one half of the depth of the longitudinal grooves. In use, rotation of the input gear wheel 14 causes relative rotation between the output drive shaft 15 and the housing 10 and thereby effects longitudinal movement of the output shaft relative to the housing. Referring to Fig. 3 there is illustrated an arrangement located in the nose region of a flight vehicle operable for controlling the flow of ram air into a duct. The arrangement includes an outer casing 20 having an inner wall 21 defining a duct, and a generally conical portion 22 mounted for movement with respect to said outer casing between a position in which they define a substantially continuous exterior surface (as illustrated in full lines) and a position in which the conical portion 22 is withdrawn to define an annular intake for ram air (as illustrated in chain dotted lines). Movement of the conical portion relative to the outer casing is effected by means of a screw jack 23 of similar form to the embodiment of Fig. 1 and similar items will be given similar references. The screw jack 23 comprises a housing 10 having one end secured to a structural member of the outer casing 20 and supporting an output shaft 15 to the outer end of which is secured the conical portion 22 by means of radial spokes 24 and thrust washers 25. The output shaft is provided with a threaded portion 16 having longitudinal grooves 17 to define a plurality of teeth. The threaded portion 16 is received in threaded bore 12 of the housing 10 and the teeth of the shaft engage the teeth of an idler gear wheel 26 rotatably mounted in the housing. The idler wheel 26 meshes with input gear wheel 14 which is driven by means of a drive motor 27 secured to the housing. Referring now to Fig. 4 the third embodiment illustrated is similar to that illustrated in Fig. 2 except that the housing is provided with an attachment lug 30 located coaxially with respect to the drive shaft 15. The threaded portion of the drive shaft extends only part-way along the length thereof and pivotally supports a U-shaped coupling member 31 by means of thrust washers 25. CLAIMS

1. A movement converting device which includes a support member including threaded bore, an elongate shaft having a threaded portion for threadedly engaging said bore, said threaded portion being provided with a plurality of elongate grooves spaced around the periphery thereof, and drive means mounted on said support member for drivably engaging said grooves, whereby operation of said drive means effects rotation of the shaft relative tq said support member thereby to effect longitudinal movement of the shaft with respect to said support member.

2. A movement converting device as claimed in claim 1, wherein said drive means includes a toothed drive wheel rotatably mounted on said support member.

3. A movement converting device as claimed in claim 1 or claim 2 wherein the drive means includes a motor mounted on said support member.

4. A movement converting device as claimed in any of the preceding claims, wherein said support member is of hollow cylindrical form including at one end an end wall having means for attachment to a further structural member.

5. A movement converting device substantially as hereinbefore described with reference to and as illustrated in any of the accompanying drawings.