EP0216959B1

EP0216959B1 - Lifting jack

Info

Publication number: EP0216959B1
Application number: EP19850201589
Authority: EP
Inventors: Isamu Aihara
Original assignee: Osaka Jack Manufacturiung Co Ktd
Current assignee: Osaka Jack Manufacturiung Co Ktd
Priority date: 1985-10-01
Filing date: 1985-10-01
Publication date: 1990-01-17
Also published as: DE3575411D1; EP0216959A1

Description

Background of the invention:

The invention relates to a lifting jack for use under heavy loads such as supporting wall structures in buildings or raising heavy loads in construction environments such as bridges, ship building and other similar works, said jack being operable from a source of rotary energy and comprising:

a rigid body defining an interior cavity, a lower base surface and a ram passage;
a beveled gear having a generally annular construction and a first circular array of teeth;
a pinion gear having a second array of teeth engageable with said first array of teeth and a pinion shaft coupling said second array of teeth to said source of rotary energy;
means supporting said pinion gear in a position of engagement with said beveled gear;
a cylindrical screw bar defining an exterior thread perpendicular to said beveled gear;
a threaded sleeve, having an interior thread cooperating with said exterior thread, engaged with and enclosing a portion of said screw bar, one of said parts being attached to said beveled gear;
a ram slidably supported within said ram passage and coupled to the other one of said parts, and a thrust bearing in said interior cavity interposed and enclosed therein between a lower surface of a part of said beveled gear and said lower base surface to take up the thrust forces transmitted by the ram to the said rigid body.

Such a lifting jack is known from a brochure called "OJ. Mechanical Jacks" put out by Osaka Jack Co., Ltd. in July 1984.
The thrust bearing of this known construction is a ball or roller bearing. Such a bearing permits the beveled gear to remain rotatable notwithstanding the substantial load imposed upon it by the weight of the subject to be lifted. Lifting jacks for heavy loads are frequently used in outdoor environments and are subjected to extreme temperatures, weathering, corrosive environments and contamination of the lubrication oil, being harmful for the proper functioning of the roller or ball bearing. An other disadvantage of the ball or roller bearing is that it requires a considerable design height increasing the overall height of the jack.
US-A 4 000 880 discloses a screw jack for lifting automobile underframes, comprising the components as mentioned in the first paragraph, however having a thrust bearing formed as a steel washer. For use under considerable load like supporting wall structures in buildings, the screw jack of US-A 4 000 880 would not work due to fact that the baffle gear does not remain rotatable under heavy load.
There is a need in the art for a lifting jack capable of bearing substantial loads by maintaining undue frictional losses and wear and tear within the device. There is a further need to provide such a structure which is suitable for use in environments where the jack is subjected to weathering or corrosive environments.

Summary of the invention.

It is a general object of the present invention to provide an improved lifting jack operable from a rotatable source of energy, said jack being suitable for use in outdoor or corrosive element environments, of which the overall jack height is minimized and of which the friction resulting from rotation of the rotatable members within the jack has such a low value that the beveled gear remains rotatable under heavy load.
In view thereof, a lifting jack as specified in the preamble of this description is characterized according to the invention in that the thrust bearing is a planar bearing formed of a polytetrafluoro-ethylene.
The most advantage embodiment of the planar bearing is one in which it is formed of multiple layers of polytetrafluoro-ethylene.
In practice the lower base surface comprises a substantially planar surface wherein said lifting jack further includes a planar plate member attached to the beveled gear supported by the planar bearing and engaging downwardly into and substantially filling said interior cavity on top of and in contact with said low friction planar bearing material.
It is remarked that a typical lifting jack with a lifting hook and an A-shaped frame is known from US-A 3 412 980 with a ball bearing between the rotary screw spindle carrying the beveled gear and its support. This jack is only suitable for rather low loads like automobiles. The support is adjustably taken up in the stationary construction by similarly shaped spherical surfaces with a layer of polytetrafluoro-ethylene between them, but only for slight mutual adjustments in position and not between force transmitting surfaces, of one rotates and the other is stationary.
By the application of the polytetrafluoro-ethylene planar bearing the rotation friction will be so much lower than would be the case by the application of a steel washer that the jack can be operated under very heavy loads, however the rotation friction in case of a polytetrafluoro-ethylene planar bearing is higher than in case of a ball or roller bearing, which happens to be an advantage as it promotes the self- braking properties, which means that the jack is kept lifted under heavy load during longer periods. There is no self-lowering.

(f) Brief Description of the Drawings:

Figure 1 is a sectioned elevation view of a lifting jack constructed in accordance with the present invention; and
Figure 2 is a partially sectioned elevation view showing details of the ratchet structure of the lifting jack.

(g) Description of the Invention:

Figure 1 shows a section view of a lifting jack constructed in accordance with the present invention. A body (17) formed of a rigid material such as cast iron or steel defines a base cavity (45) and a cylindrical ram passage (41) and a pinion passage. The latter is generally perpendicular to ram passage (41) for reasons set forth below in greater detail. Body (17) further defines a circular threaded passage (55) which is generally concentric with ram passage (41). A generally cylindrical base (28) defines a base surface (82) and an upwardly extending wall (53). Wall (53) defines an external thread (54) which cooperates with thread (55) of body (17) to secure and attach base (28) to the lower end of body (17). Base (28) provides the resting surface for the lifting jack and defines a bearing surface (67) on its interior. Bearing surface (67) is generally flat and recessed in correspondence with wall (53). A plate (83) having a substantially annular construction is received within the interior of base (28) and overlies bearing surface (67). Plate (83) defines a planar bearing surface (68). A sliding pad (29) formed of a fluorine resin material such as Teflon (Trademark of DuPont) or similar self-lubricating low friction material of polytetrafluoro-ethylene is interposed between bearing surfaces (67 and 68) in accordance with an important aspect of the present invention.
A beveled gear (67) having a structure generally in accordance with the prior art defines a plurality of angularly positioned teeth (50) and a center aperture. Beveled gear (27) rests upon and is attached to plate (83). A generally cylindrical elongated screw bar (14) defines an external thread (47) for the upward portion of its length and terminates at its lower end in a rim (48) having a generally cylindrical construction and extending beyond the perimeter of threads (47). Screw bar (14) further defines an extension (62) having a generally cylindrical shape which passes through said aperture in beveled gear (27). Rim (48) further defines a surface (51) which rests upon beveled gear (27). A bond (86) which may for example comprise a weld bead encircles the junction of rim (48) and beveled gear (27) to insure a complete attachment therebetween. As a result, rotation of beveled gear (27) causes a corresponding angular rotation of screw bar (14). A generally cylindrical ram (16) having a substantially hollow construction and formed of a rigid material such as steel, is received within ram passage (41) and defines a thread (43) over a portion of its upper inner surface.
A threaded sleeve (21) having an exterior surface substantially conforming to the interior surface of ram (16) and an internal thread (46) which corresponds to thread (47) of screw bar (14) is received within a cavity (87) of ram (16), said cavity having a shoulder part at its top. A set screw (15) is received between ram (16) at cavity (87) and threaded sleeve (21) to secure the attachment of this sleeve (21) to ram (16). A head (10) having a generally cylindrical construction defines a center aperture (4) and a downwardly extending threaded portion (42). The latter cooperates with thread (43) of ram (16) to secure head (10) to ram (16). A set screw (12) is received within ram (16) and abuts threaded portion (42) of head (10) to secure the attachment between head (10) and ram (16). A flathead screw (11) is received within aperture (4). Head (10) further defines a load surface (39).
Ram (16) further defines a channel (89) extending vertically over its entire length. Body (17) further defines a pair of apertures in its upper wall which receive a pair of bolts (18 and 19). A key having a configuration permitting it to be slidably received within channel (89) is secured to body (17) by the engagement of bolts (18 and 19) into threaded apertures (79). As ram (16) is moved vertically with respect to body (17) channel (89) moves with respect to said key. The cooperation of this key with channel (89) inhibits rotation of ram (16) which would otherwise take place due to the friction between thread (46) and (47) of threaded sleeve (21) and screw bar (14) respectively.
Body (17) further defines a pinion extension extending outwardly and generally perpendicular to ram passage (16) which defines a cylindrical pinion passage. A cylindrical pinion bushing (24) is received within said pinion passage. A set screw (20) is engaged between pinion bushing (24) and said pinion passage to secure the former to the latter. A pinion gear (90) having a construction generally corresponding to the typical pinion gear in the art defines a plurality of angled teeth (66) which are configured in correspondence to teeth (50) of beveled gear (27). Pinion gear (90) further defines a pinion shaft (73) which extends outwardly through said pinion passage and is supported by pinion bushing (24). An annular thrust washer (80) is positioned between pinion gear (90) and pinion bushing (24) to position and support pinion gear (90) with respect to the axial thrust forces imposed by rotation of the gears under load. Pinion shaft (73) further defines a multi-facetted portion (74) having a generally hexagonal construction and a cylindrical terminating portion.
A ratchet wheel (25) having a construction shown more clearly in Figure 2 is taken up in ratchet receptacle (72) and is configured to engage and be supported by the multy-facetted portion (74) of pinion shaft (73). Ratchet wheel (25) includes a plurality of external teeth. A ratchet case (30) having a generally cylindrical construction surrounds ratchet wheel (25) and receives the extension of pinion shaft (73). A washer (23) is received upon pinion shaft (73) and a snap ring (26) engages the end portion of pinion shaft (73) to secure ratchet case (30) with respect to body (17) and pinion shaft (73). In accordance with well-known construction for rotatable ratchet drives, ratchet (92) provides a bi-directional ratcheting function in which rotation of ratchet case (30) may selectively be coupled in a ratcheting fashion to pinion shaft (73) in either direction. The structure of ratchet (92) is known in the prior art and therefore need not be described in great detail in connection with this invention. Suffice it to say however, that ratchet case (30) defines a lateral passage which receives a ratchet liner (34), a ratchet plunger (35), is received with liner (34) and defines a plurality of teeth (93) which are configured to cooperate with and engage the teeth of ratchet wheel (25) when ratchet plunger (35) is moved to engagement with ratchet wheel (25). Liner (34) further defines a detent aperture (76). A housing (37) formed in ratchet case (30) defines an aperture (95) generally perpendicular to liner (34). A steel ball (31) is supported within aperture (95). A spring (32) is within aperture (95). A set screw (33) captivates spring (32) in a compressive state against steel ball (31). The resulting structure forms a spring loaded detent mechanism which cooperates to maintain liner (34) and thereby ratchet plunger (35) in a fixed position.
Ratchet case (30) also defines a bar socket (70) extending downwardly from pinion shaft (73) and defining a cylindrical cavity (71). In accordance with commonly employed use of lifting jacks, cavity (71) receives a lever bar which permits the application of a substantial torque force to bar socket (70) and ratchet plunger (35). Depending upon the position of liner (34), ratchet plunger (35) or its counterpart (not shown) will be in engagement with the teeth of ratchet wheel (25): The applied force to bar socket (70) will be coupled by the ratchet plunger engaging the ratchet wheel to turn pinion shaft (73). Ratcheting action is provided by the. cooperation of ratchet plunger (35) and spring (36). A plate (77) is received within ratchet case (30) to complete the enclosure of the ratchet structure.
In operation, the application of a lever force to bar socket (70) causes a corresponding torque to be applied to ratchet case (30). As mentioned above and depending upon which ratchet plunger (35) is moved into engagement with ratchet wheel (25), a corresponding torque is applied to ratchet wheel (25) and in turn to pinion shaft (73). The torque imposed on pinion shaft (73) is coupled by teeth (66) and teeth (50) to bevel gear (27). The torque applied to beveled gear (27) due to the attachment of bevel gear (27) to screw bar (14) causes rotation of screw bar (14). Due to the cooperation of threads (46 and 47) in threaded sleeve (21) and screw bar (14) respectively, threaded sleeve (21) is driven upwardly carrying ram (16) with it. The upward travel of ram (16) due to rotation of screw bar (14) causes surface (39) of head (10) to contact the load and drive it upward.
The resulting load force imposed by the foregoing described action is borne by beveled gear (27) and is in turn transmitted to plate (83). The load imposed upon plate (83) is in turn transmitted to sliding pad (29) and base (28). Because base (28) is supported in the normal operation by some fixed support, the resulting effect of the foregoing described operation places a compressive force upon sliding pad (29). In accordance with an important aspect of the present invention, sliding pad (29) receives the compressive force and due to its low coefficient of friction distributes such force while still permitting beveled gear (27) and plate (83) to rotate with respect to base (28).
As will be apparent to those skilled in the art, the resulting structure in operation provides for imposition of substantial loads upon head (10) while maintaining a relatively low friction coupling between sliding pad (29) and base (28) and plate (83) and bevel gear (27). It will also be apparent to those skilled in the art that sliding pad (29) is substantially thinner than the prior art bearing structures and as a result reduces the overall height of the lifting jack. In further advantage the use of sliding pad (29) is not substantially affected by the presence of moisture or corrosive materials due to its inherent low friction non-metallic composition. In further advantage, no lubricant is necessary to maintain the low friction bearing surface provided by sliding pad (29).
While the foregoing has illustrated and described what is now contemplated to be the best mode of carrying out the invention, the description is, of course, subject to modifications without departing from the scope of the invention. Therefore, it is not desired to restrict the invention to the particular constructions illustrated and described, but to cover all modifications that may fall within the scope of the appended claims.

Claims

1. A lifting jack for use under heavy loads such as supporting wall structures in buildings or raising heavy loads in construction environments such as bridges, ship building and other similar works, said jack being operable from a source of rotary energy and comprising:

a rigid body (17) defining an interior cavity (45), a lower base surface (82) and a ram passage (41);

a beveled gear (27) having a generally annular construction and a first circular array of teeth (50);

a pinion gear (90) having a second array of teeth engageable with said first array of teeth and a pinion shaft (73) coupling said second array of teeth to said source of rotary energy;

means (24) supporting said pinion gear (90) in a position of engagement with said beveled gear (27);

a cylindrical screw bar (14) defining an exterior thread perpendicular to said beveled gear (27);

a threaded sleeve (21), having an interior thread cooperating with said exterior thread, engaged with and enclosing a portion of said screw bar (14), one of said parts being attached to said beveled gear (27);

a ram (16) slidably supported within said ram passage (41) and coupled to the other one of said parts, and a thrust bearing (29) in said interior cavity interposed and enclosed therein between a lower surface of a part of said beveled gear (27) and said lower base surface (82) to take up the thrust forces transmitted by the ram (16) to the said rigid body (17), characterized in that the thrust bearing (29) is a planar bearing formed of a polytetra-fluoro-ethylene material.

2. A lifting jack as set forth in claim 1, wherein said lower base surface (28) comprises a substantially planar surface and wherein said lifting jack further includes a planar plate member (83) attached to said beveled gear (27) supported by said planar bearing (29) and engaging downwardly into and substantially filling said interior cavity (45) on top of and in contact with said low friction planar bearing material (29).

3. A lifting jack as set forth in any of the preceding claims wherein said planar bearing (29) is formed of multiple layers of polytetra-fluoro-ethylene.