GB2206330A - Jack - Google Patents

Abstract

A jack comprises a tubular casing (10) and a bush (24) which is an interterence fit in the end of the casing (10) remote from a base (12). Bearings (28) supported by the bush (24) rotatably mount a nut (14) coaxially with the casing (10); a crown gear (16) is coaxially secured to the nut. A pinion (18), carried in a pre-assembled bearing assembly (38) which can be slidingly inserted in a housing (42) secured to the casing (10) to retain the assembly (38) in place, is in mesh with the crown gear (16) for rotating the nut (14). Screw means (20) having load engaging means (22) is housed coaxially in driving engagement with the nut (14). Spring means (30) comprising fingers (36) engaging the screw means (20) prevent the screw means (20) rotating with the nut (14) when the jack is not under load. <IMAGE>

Description

JACKS This invention is concerned with jacks and especially jacks of the general type described in our patent No. 1341363, commonly referred to as bottle jacks.

The jacks described by way of example in our aforesaid patent have proved to be satisfactory in operation. However they are rather complicated and expensive to manufacture, manufacture involving, as it does, a considerable amount of welding and rather intricate assembly work.

It is one of the various objects of the present invention to provide an improved jack.

In one aspect the invention may be considered to provide a jack comprising a tubular casing have a base at one end, a nut rotatably mounted on the casing, a crown gear coaxially secured to the nut, operating means including a pinion in mesh with said crown gear for rotating the nut, screw means housed in the casing and in driven engagement with the nut and having load engaging means thereon at an end portion remote from the base, and means mounting the nut on the casing comprising a bush which is an interference fit in the end portion of the casing remote from the base.

Suitably the bush provides a bearing track for bearings by which the crown gear, and thus the nut, is supported.

Preferably a jack according to the invention comprises spring means arranged to engage the screw means with sufficient force te prevent the screw means rotating with the nut when the jack is not under load. The spring means preferably comprises an annular portion supported on a shoulder in the casing and spring fingers extending inwardly from the annular portion with their inner end portions urged against the screw means; suitably the fingers are inclined downwardLy as well as inward) towards the screw means so that, should the screw means leave the region of the fingers as the jack is raised, when it is lowered again the inclined fingers will provide a channel allowing the screw means to readily re-enter the passage between the fingers.

In another aspect the invention may be considered to provide a jack comprising a tubular casing have a base at one end, a nut rotatably mounted on the casing, a crown gear coaxially secured to the nut, operating means including a pinion in mesh with said crown gear for rotating the nut, screw means housed in the casing and in driven engagement with the nut and having load engaging means thereon at an end portion remote from the base, and spring means arranged to engage the screw means with sufficient force to restrain the screw means from rotating with the nut when the jack is not under load, the spring means comprising an annular portion supported on a shoulder in the casing and spring fingers extending inwardly from the annular portion with their inner end portions urged against the screw means.

In a further aspect, the invention may be considered to provide a jack comprising a tubular casing have a base at one end, a nut rotatably mounted on the casing, a crown gear coaxially secured to the nut, operating means including a pinion in mesh with said crown gear for rotating the nut, screw means housed in the casing and in driven engagement with the nut and having load engaging means thereon at an end portion remote from the base, and a bearing assembly mounted on the casing and rotatably mounting the pinion, the bearing assembly being preassembled before being mounted to the casing and comprising a bearing bush adapted to be slidingly inserted into a housing attached to the casing, an axle supported for rotation by the bush and the pinion, secured to the axle.

The bearing bush is preferably made of a material which is chosen to be of suitable hardness and wearing properties and conveniently may be made of any suitable plastics material commonly used for this purpose, for example nylon.

Conveniently the pinion is secured to the axle by providing a portion on the axle of an irregular shape which is, in assembly, slidingly received in a complementary hole in the pinion so that pinion and axle rotate as a unit, with a tip of the axle projecting beyond the pinion. Suitably the projecting portion may be headed to retain the pinion in place. The axle conveniently has a head at the end opposite the pinion to retain it in the bearing bush.

A socket member by which a handle can be engaged to rotate the pinion is secured to the pinion e.g. by welding.

Conveniently the bearing bush is formed in two mating parts which can be slid into place around the axle after the pinion has been attached to the axle and the socket member has been attached to the pinion, thereby eliminating the possibility of damage to the bush which might arise from the heat of a welding operation on the socket member or the physical impact of a heading rtion.

Preferably the bearing bush comprises means, e.g.

lugs which engage in corresponding holes in the housing, by which the bush is retained in place in the housing.

There now follows a detailed description to be read with reference to the accompanying drawings, of a jack embodying the invention. It will be realised that this jack has been selected for description to illustrate the invention by way of example.

In the accompanying drawings: Figure 1 is a view, mainly in section, of a jack embodying the invention; Figure 2 is a side view of spring means of a jack according to the invention; Figure 3 is a plan view of the spring means shown in Figure 2; Figures 4a - 4c are respectively plan orthogonal side views of a bearing bush of the bearing assembly of the illustrative jack; Figures 5a and 5b are, respectively, views in section and in plan of a pinion of the bearing assembly; Figures 6a and 6b are, respectively, side and plan views of an axle of the bearing assembly; Figures 7a and 7b are, respectively, a plan view and two orthogonal side views of a housing for the bearing assembly; and Figure 8 is a view in section of a plug portion of a bush of the illustrative jack.

The illustrative jack is, in many ways, similar to the jack described in our Patent No. 1341363, but has a number of differences which reduce the amount of welding involved, the complexity of manufacture, improve the performance, and reduce the manufacturing costs to some extent. The illustrative jack comprises a tubular casing 10 of circular cross-section having a base 12 at one end; a nut 14 is rotatably mounted on the casing; a crown gear 16 is coaxially secured to the nut 14 e.g. by welding.

Crown gear 16 is arranged to be rotated, when the jack is in use, by a pinion 18 meshing with the crown gear, the pinion being arranged to be rotated by a socket member 19 secured to the pinion 18, into which a suitable operating handle may be inserted to rotate the pinion; other means for rotating the pinion may be provided, instead, if desired.

Screw means 20 is housed, coaxially, in the casing 10. In the illustrative jack the screw means 20 comprises an inner rod and an outer tube the outer tube being screw threaded in the nut 14 in a manner similar to that described with reference to Figure 3 of the drawings of our Patent No. 1341363. However, the number of concentric tubes to provide the screw means can be varied and is dependent upon the amount of extension required of the jack. Although the tubular casing 10 is of circular cross-section, the casing may be of any convenient shape in cross-section, for example circular, square or fluted; the casing 10 may be formed likewise, in any convenient way, for example by forming a metal pressing, by extrusion, or by drilling metal.

The illustrative jack further comprises load engaging means 22, at the end portion remote from the base 12, the load engaging means being constructed to support axles of varying shapes; any convenient load engaging means may be provided in a jack generally similar to the illustrative jack, according to the invention.

The nut 14 is mounted for rotation on the casing 10 by means comprising a bush 24 which is an interference fit in the end portion of the casing 10 remote from the base 12. The bush 24 may conveniently be provided with a plug portion 25 which, in cross-section, is of generally sllOed ^ped shape The amount of scalloping provided is selected so that the plug portion 25 can be press fitted into the end portion of the casing 10 without it being necessary to use an excessive amount of force but to provide sufficient engagement with the casing 10 to render the accidental removal of the bush 24 extremely unlikely. If desired, the plug portion 25 of the bush may be of circular outer cross-section, giving a very tight interference fit with the casing 10.

An upper flange of the bush 24 provides a bearing track for bearings 28 which engage a bearing track secured beneath the crown gear 16, thereby supporting the nut 14 for rotation. The amount by which the bush 24 can be inserted into the casing is determined by engagement of the flange of the bush with the upper end portion of the casing. The nut 14 comprises a tubular central portion 15 having latch lugs 17 at the end thereof remote from the crown gear: the tubular central portion 15 may be slidingly inserted in the central opening of the bush 24, the latch lugs at the lower end of the portion 15 springing outwardly, to latch beneath the uppermost portion of the bush to prevent the nut 14 becoming disassembled from the casing 10.

The illustrative jack further comprises spring means 30, the spring means of the illustrative jack comprising an annular portion (see Figures 2 and 3, especially,) and spring fingers 36 which, when the spring means 30 is assembled in the illustrative jack, are inclined downwardly and inwardly towards the screw means 20. The spring means 30 is supported on a shoulder provided by a number of lugs 37 formed in the tubular casing by cutting and pressing metal of the casing inwardly. As can be seen from Figure 1, the spring means 30 can be placed on the lugs 37 before the bush 24 is inserted in the tubular casing and the spring means 30 is retained in place by the bush 24 and lugs i7 of the nat 14.When the screw means is in the retracted position (in which it is shown in Figure 1) the spring fingers are urged against the outer surface of the screw means (see Figure 1): by engagement of the spring fingers 36 of the spring means 30 with the screw means 20 sufficient frictional force is applied to the screw means 20 to prevent the screw means 20 rotating with the nut 14 when the nut 14 is rotated but the jack is not under load (as would be, for example, the case when the jack has been positioned beneath a part of a vehicle to be lifted but not yet extended sufficiently for the load engaging means 22 to actually engage the vehicle).Screw means 20 comprise stops 21 which, as the various parts of the screw means are raised to their fullest extent engage shoulders to prevent the part of the screw means being further raised: for example the stop 21 at the outer part of the screw means will engage a shoulder provided on the inner surface of the nut 14.

The screw means may be raised, by rotation of the nut 14, to such an extent, that they leave the passageway between the spring fingers 36: because the spring fingers 36 are inclined downwardly as well as inwardly towards the screw means 20, when the screw means 20 is lowered again, the inclined fingers 36 provide a tapered lead-in channel which allows the screw means 20 to readily re-enter the passage between fingers 36.

As hereinbefore described, the illustrative jack comprises a pinion 18 which is in meshing engagement with the crown gear 16 and which may be rotated to rotate the crown gear and nut 14 to raise or lower the screw means 20 of the jack. The pinion 18 is supported for rotation by a bearing assembly which is conveniently pre-assembled as a sub-assembly for subsequent mounting on the casing 10. In order to mount this bearing assembly 38 on the casing 10, a housing 42 is secured, for exa.r.r'e by welding, to the tubular casing 10.

The bearing assembly itself comprises a bearing bush 40, conveniently manufactured in two halves, and an axle 44 to which the pinion 18 is secured. In making the bearing assembly, the pinion 18 is first mounted on the axle 44: conveniently a portion of irregular shape, for example the flatted end portion 46 (see Figure 6) is provided on the outer end portion of the axle 44 and is slidingly received in a complementary hole in the pinion 18. The flatted portion 46 comprises a flat 48 on one side, the rest of the portion 46 being of circular crosssection but of a reduced diameter compared with the remainder of the axle 44.The pinion 18 may therefore-be mounted on the axle by inserting the flatted portion 46 in the complementary opening in the pinion until the pinion engages the shoulder formed at the junction of the flatted portion 46 with the remainder of the axle. The flat 48 ensures that the pinion 18 and axle 44 rotate as a unit. After the pinion 18 has been mounted on the axle 44 in this way, the pinion 18 is secured to the axle 44, conveniently by heading the outermost end portion of the flatted portion 46, for example by spin rivetting. After the pinion 18 has been attached to the axle the socket member 19 is secured to the pinion, conveniently by a simple welding operation.

Following the attachment of the pinion 18 to the axle 44, the bearing bush 40 is assembled on the axle.

The bush 40 is manufacturered (as can be seen from Figure 4) in two parts so that the two parts may be inserted at either side of the axle 44 to provide a bearing opening supporting the axle 44. The axle 44 has a headed portion 45 at its inner end which i received in a recess of the bearing bush 40 (see Figure 1). Although in the illustrative jack the bush 40 is made in two parts and is mounted to the remainder of the bearing assembly 38 after the pinion 18 has been attached to the axle and socket member 19 has been attached to the pinion, the bearing bush 40 may be made in one piece and assembled onto the axle 44 before the pinion 18 is attached. However, in that event, there is a considerably increased risk that the bearing bush 40 will be damaged by heat or by the impact which arises when the pinion is attached to the axle 44 or when the socket member 19 is welded to the pinion 18.

After the bearing assembly 38 has been formed into a sub-assembly as described above, the bearing bush 40 is inserted into the housing 42 in which it is a snug, sliding fit. As can be seen from the drawings, especially Figures 4, 7 and 1, the housing is shaped to provide an opening complementary to the bearing bush 40, within which the bush 40 can be slidingly received. The bearing bush 40 is provided with opposed lugs 52 which are adapted to engage corresponding holes 54 provided in the housing 42. The lugs are compressed as the bearing bush 40 is pressed into the housing 42 and spring into place in the holes 54 to latch the bearing bush 40 in place and retain it in the housing 42. The axle 44 (to which the pinion 18 is attached) is retained in place by the head 45; as can be seen from the drawings the housing 42 is of square cross-section as is the bearing bush 40.The faces of the housing 42 and bearing bush 40 are shaped to seat snugly on the casing 10 (see especially Figures 4c and 7c).

The bearing bush 40 is formed of a suitable plastics material of a hardness and wearing properties suitable for withstanding the loads which will be applied during operation of the illustrative jack, for example a suitable grade of nylon or other plastics material.

As can be seen from the previous description, the amount of welding involved in the manuàcture of tisE illustrative jack is small and the jack may be assembled simply and efficiently. By reason of the elimination of welding and the simplification of the assembly of the illustrative jack the cost of manufacture of the jack may be reduced and the time taken to assemble a jack likewise reduced. In addition, by provision of the spring means 30, a simple and efficient way of applying sufficient frictional force to the screw means 32 to restrain it from rotating with the nut 14 when the jak is not under load is provided, this spring means 30 being readily assembled in the manufacture of the jack.

Claims (15)

1. A jack comprising a tubular casing have a base at one end, a nut rotatably mounted on the casing, a crown gear coaxially secured to the nut, operating means including a pinion in mesh with said crown gear for rotating the nut, screw means housed in the casing and in driven engagement with the nut and having load engaging means thereon at an end portion remote from the base, and means mounting the nut on the casing comprising a bush which is an interference fit in the end portion of the casing remote from the base.

2. A jack according to Claim 1 wherein the bush provides a bearing track for bearings by which the crown gear and nut are supported.

3. A jack according to either one of Claims 1 and 2 comprising spring means arranged to engage the screw means with sufficient force to prevent the screw means rotating with the nut when the track is not under load.

4. A jack according to Claim 3 wherein the spring means comprises an annular portion supported on a shoulder in the casing and spring fingers extending inwardly from the annular portion with their inner end portions urged against the screw means.

5. A jack comprising a tubular casing have a base at one end, G nut rotatably moated on the casing, a crn gear coaxially secured to the nut, operating means including a pinion in mesh with said crown gear for rotating the nut, screw means housed in the casing and in driven engagement with the nut and having load engaging means thereon at an end portion remote from the base, and spring means arranged to engage the screw means with sufficient force to restrain the screw means from rotating with the nut when the jack is not under load, the spring means comprising an annular portion supported on a shoulder in the casing and spring fingers extending inwardly from the annular portion with their inner end portions urged against the screw means.

6. A jack comprising a tubular casing have a base at one end, a nut rotatably mounted on the casing, a crown gear coaxially secured to the nut, operating means including a pinion in mesh with said crown gear for rotating the nut, screw means housed in the casing and in driven engagement with the nut and having load engaging means thereon at an end portion remote from the base, and a bearing assembly mounted on the casing and rotatably mounting the pinion, the bearing assembly being preassembled before being attached to the casing and comprising a bearing bush adapted to be slidingly inserted into a housing attached to the casing, an axle supported for rotation by the bush and the pinion, secured to the axle.

7. A jack according to any one of Claims 1 to 5 comprising a bearing assembly mounted on the casing and rotatably mounting the pinion, the bearing assembly being pre-assembled before being attached to the casing and comprising a bearing bush adapted to be slidingly inserted into a housing attached to the casing, an axle supported for rotation by the bush and the pinion, secured to the axle.

S. jacii according to either one of Claims 6 and 7 wherein the bearing bush is made of a suitable plastics material.

9. A jack according to any one of Claims 6 to 8 wherein the pinion is secured to the axle by providing a portion on the axle of irregular shape which is, in assembly slidingly received in a complementary hole in the pinion.

10. A jack according to Claim 9 wherein the pinion is retained on the axle by heading a projecting portion of the axle.

11. A jack according to any one of Claims 6 to 10 wherein the axle has a head at the inner end to retain the axle in the bearing bush.

12. A jack according to any one of Claims 6 to 11 wherein the bearing bush is manufactured in two mating parts which can be slid into place around the axle after the pinion has been attached to the axle to provide the bearing assembly.

13. A jack according to any one of Claims 6 to 12 comprising interengaging means on the bearing bush and housing by which the bush is retained in place in the housing.

14. A jack according to Claim 13 wherein the means comprise lugs on the bearing bush which engage in corresponding holes in the housing.

15. A jack constructed, arranged and adapted to operate substantially as hereinbefore described with reference to the accompanying drawings.