SCREW JACK

VERIN

English Abstract

A screw jack comprising a bed, a case body having a groove formed therein and mounted on an upper surface of the bed, and a thrust bearing mounted on a central area of the upper surface of the bed. A large bevel gear is placed on the bed through the thrust bearing such that a main threaded shaft of the large bevel gear is secured at a lower end thereof to the thrust bearing and erected upwardly therefrom. A small bevel gear carried on the case body through a bearing meshes with the large bevel gear. An outer sleeve is guided along the groove of the case body. A heavy object raising inner sleeve is disposed within the outer sleeve and is guided by the outer sleeve. The main threaded shaft is rotated through the large bevel gear by the small bevel gear which is rotated by an external driver so that a heavy object is raised. The case body is integrally formed of aluminum casting or hard resin.

French Abstract

Un cric à vis comprenant un lit, un boîtier ayant un sillon et monté sur une surface supérieure du lit et un palier de butée monté sur une zone centrale de la face supérieure du lit. Une grande roue conique est placée sur le lit à travers le palier de butée de manière à ce qu'une tige filetée principale de la grande roue conique soit fixée à une extrémité inférieure du palier de butée et érigée vers le haut à partir de celui-ci. Une petite roue conique entraînée sur le corps du boîtier grâce à un roulement s'engrène avec la grande roue conique. Une gaine externe est guidée le long de la rainure du corps du boîtier. Une gaine interne servant à soulever les objets lourds est disposée dans la gaine externe et est guidée par la gaine externe. La tige filetée principale est tournée sur la grande roue conique avec la petite roue conique qui est tournée par un élément externe pour soulever un objet lourd. Le corps du boîtier est intégralement constitué d'aluminium coulé ou de résine dure.

Claims

9
The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A screw jack comprising a bed; a case body having a
groove formed therein and mounted on an upper surface of said
bed; a thrust bearing mounted on a central area of the upper
surface of said bed; a large bevel gear placed on said bed
through said thrust bearing such that a main threaded shaft of
said large bevel gear is secured at a lower end thereof to
said thrust bearing and erected upwardly therefrom; a small
bevel gear carried on said case body through a bearing and
meshed with said large bevel gear; an outer sleeve guided
along the groove of said case body; and a heavy object raising
inner sleeve disposed within said outer sleeve and guided by
said outer sleeve; said main threaded shaft being rotated,
through said large bevel gear, by said small bevel gear which
is rotated by an external driver means, so that a heavy object
is raised, wherein said case body is integrally formed of
aluminum casting or hard resin.
2. A screw jack including an outer sleeve guided along a
case body and adapted to guide a heavy object raising inner
sleeve, wherein said outer sleeve is formed by bending a
planar plate into a tubular shape and overlapping and jointing
opposite end faces of said tubular-shaped plate such that the
jointed portion projects outwardly, the projected jointed
portion being fitted in a groove vertically formed in said
case

Description

21'~0~4.a
TITLE OF THE INVENTION
SCREW JACK
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a screw jack, which is also known
as j ackscrew, used for raising heavy obj ects such as
automobiles and the like.
2. Brief Description of the Prior Art
1o Heretofore, there are widely used screw j acks of the type
in which a case body portion is of steel plate construction or
of a rigid construction of FC casting. Usually, an outer sleeve
part contacting the case body is a molded product having a
tubular configuration. The outer sleeve is provided with a key
15 groove so that the sleeve will not rotate.
However, the above conventional screw jacks have the
following shortcomings. In the case of the screw jacks of steel
plate construction, the screw jacks are comprised of a
plurality of component parts and therefore; the steps for
20 manufacturing such component parts are required. This '
eventually results in high cost. In the case of the screw jacks
of a rigid construction of FC casting, the weight of final
products tends to be increased.
Moreover, since the component part serving as the outer

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sleeve which contacts the case body is subjected to key groove
treatment in order to prevent the outer sleeve from rotating
with the use of the groove, the steps for manufacturing such
key grooves are required. Furthermore, there is a need of
using an outer sleeve part having a thick wall enough to be
subjected to key groove treatment. The use of an outer sleeve
part having a thick wall makes it even difficult to lower the
manufacturing cost and also to reduce the weight of final
products.
The present invention has been accomplished in view of
the above situation.
SUMMARY OF THE INVENTION
The present invention provides a screw jack which is
simple in construction, light in weight and inexpensive to
manufacture.
According to the present invention, there is provided a
screw jack comprising a bed; a case body having a groove
formed therein and mounted on an upper surface of said bed; a
thrust bearing mounted on a central area of the upper surface
of said bed; a large bevel gear placed on said bed through
said thrust bearing such that a main threaded shaft of said
large bevel gear is secured at a lower end thereof to said
thrust bearing and erected upwardly therefrom; a small bevel
gear carried on said case body through a bearing and meshed
with said large bevel gear; an outer

21709a
3
sleeve guided along the groove of the case body; and a heavy
object raising inner sleeve disposed within the outer sleeve
and guided by the outer sleeve; the main threaded shaft being
rotated, through the large bevel gear, by the small bevel gear
which is rotated by an external driver means, so that a heavy
object is raised, wherein the case body is integrally formed of
aluminum casting or hard resin.
From another aspect of the invention, there is also
provided a screw j ack including an outer sleeve guided along a
1o case body and adapted to guide a heavy object raising inner
sleeve, wherein the outer sleeve is formed by bending a planar
plate into a tubular shape and overlapping and jointing
opposite end faces of the tubular-shaped plate such that the
j ointed portion proj ects outwardly, the proj ected j ointed
portion being fitted in a groove vertically formed in the case
body so that the outer sleeve is prevented from rotating.
The above and other objects and attendant advantages of the
present invention will be apparent to those skilled in the art
from a reading of the following description and claims in
conjunction with the accompanying drawings which constitute
part of this specification.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a vertical sectional side view of a screw jack
according to one embodiment of the present invention;

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4
Fig. 2 is a side view, partly cut-away, of only a case body
of the screw jack of Fig. 1;
Fig. 3 is a plan view of the case body;
Fig. 4 is a side view of an outer sleeve of the screw jack
of Fig. 1;
Fig. 5 is a plan view of the outer sleeve; and
Fig. 6 is a plan view showing a relation between the case
body and the outer sleeve.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
One preferred embodiment of a screw j ack according to the
present invention will now be described in detail with
reference to the accompanying drawings.
Reference numeral 1 denotes a case body of the screw jack.
This case body 1 is integrally formed of aluminum casting or
hard resin. Reference numeral 2 denotes a bed of a generally
square shape, which is made of steel material: A recess 2a is
formed in a central area of an upper surface of the bed 2. The
recess 2a is such dimensioned that when the bed 2 is placed on
2o the contacting ground surface W, a bottom surface of the recess
2a is flush with the ground surface W. The case body 1 is '
mounted on the bed 2 with a flange portion of the case body 1
firmly secured to the surface of the bed 2 with rivets ( not
shown ) or the like .
A thrust bearing 3 is disposed in the recess 2a of the bed

2~7~~4~0
2 and a large bevel gear 5 is placed on the thrust bearing 3.
A lower end of a main threaded shaft 4, which is provided with
a threaded portion 4a in an outer periphery thereof, is fixed
to the large bevel gear 5, for example, by means of knocking and
the main threaded shaft 4 is erected upwardly from the large
bevel gear 5. The large bevel gear 5 is meshed with a small
bevel gear 6 on a shaft 6a which is carried on a bearing portion
la integrally formed on the case body 1. The bearing portion la
is located on an inclined line ( not shown ) connecting the
center of the large bevel gear 5 and the center of the shaft 6a.
A handle joint 7 is provided on one end of the shaft 6a.
The handle j oint 7 is rotated by a suitable external driving
means, so that a rotational force is transmitted to the large
bevel gear 5 through the small bevel gear 6.
The threaded portion 4a of the main threaded shaft 4 is
engaged with a threaded portion 8a formed on an inner side of a
lower part of an auxiliary threaded sleeve 8. A threaded
portion 8b on an outer periphery of the auxiliary threaded
sleeve 8 is engaged with a threaded portion 9a formed on an
2o inner side of a lower part of a heavy object raising inner
sleeve 9. The inner sleeve 9 is provided with a groove 9b
formed in an outer periphery thereof and extending in a
vertical direction of the inner sleeve 9. An engagement
portion 10a as later described is formed, by knocking, on an
upper part side of an outer sleeve 10 in such a manner as to

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project inwardly. The engagement portion 10a is engaged in the
groove 9b in order to prevent rotation of the heavy object
raising inner sleeve 9 and also to guide the inner sleeve 9 when
the inner sleeve 9 is lifted upwardly and downwardly.
A receiving metal piece 11 is rotatably fitted to an upper
end of the heavy object raising inner sleeve 9 through a ring or
the like. The receiving metal piece 11 is adapted to receive a
heavy object, when placed thereon, such as, for example,
automobile or the like. The outer sleeve 10 is formed by a
1o Planar steel plate. The planar steel plate is bent and formed
into a tubular shape. Then, flat surface portions a, and b on
opposite side edges of the steel sheet are overlapped and
welded c such that the welded portion pro j ects outwardly,
thereby defining a key portion 10b. The outer sleeve 10 is
provided on an upper portion of the other side thereof with an
engagement portion 10a for engaging in the groove 9b of the
inner sleeve 9 and on a lower end thereof with an escape
preventive portion 10c protruding outwardly, so that a stopper
lc formed on an inner wall of the case body 1 is engaged
2o therewith, thereby to prevent the outer sleeve 10 from escaping
upwardly by restricting a further upward movement of the outer
sleeve 10.
The key portion 10b of the outer sleeve 10 is fitted in the
vertical groove lb formed in the inner wall of the case body 1,
so that the outer sleeve 10 is prevented from rotation and so

2~70~~0
that the heavy object raising inner sleeve 9 is prevented from
rotation through the engagement portion 10a of the outer sleeve
10.
Owing to the above-mentioned arrangement, when the large
bevel gear 5 of the main threaded shaft 4 erected upwardly from
the thrust bearing 3 located on the center of the bed 2 is
rotated by rotating the small bevel gear 6 which is meshed with
the large bevel gear 5 and carried on the bearing portion la of
the case body 1 with the handle joint 7 disposed outside the
case body 1, the main threaded shaft 4 is rotated through the
main bevel gear 5. Rotation of the main threaded shaft 4 causes
the auxiliary threaded sleeve 8 to gradually move upwardly
because the threaded portion 8a of the auxiliary threaded
sleeve 8 is meshed with the threaded portion 4a of the main
threaded portion 4 and because the auxiliary threaded sleeve 8
is guided by the outer sleeve 10 which is guided by the case
body 1. In this way, the heavy object such as automobile loaded
on the receiving metal piece 11 is finally raised. That is, the
outer sleeve 10 is caused to stop rotation by the case body 1
2o and the heavy abject raising inner sleeve 9 is also caused to
stop rotation through the outer sleeve 10. Accordingly,
rotation of the main threaded portion 4 is transmitted
gradually to the heavy object raising inner sleeve 9, thereby
raising and lowering the heavy object loaded on the receiving
metal piece 11.

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As described hereinbefore, the case body is integrally
formed of aluminum resin or hard resin. Accordingly, the
number of component parts and working processes can be reduced.
Also, in the outer sleeve portion, a planar plate is bent and
formed into a tubular shape and the faces of the opposite end
sides of the tubular shaped plate are overlapped and j ointed
such that an outwardly protruded portion thereof forms a key
portion. Accordingly, there is no need of a provision of a key
groove, the material can be made thinner, and the number of
1o manufacturing processes can be reduced. Incidentally, today,
exhaust gas of automobiles comes to be a social problem in view
of air pollution. Thus, there is a strong requirement for
making automobiles lighter in weight as much as possible. The
screw j ack according to the present invention can fully meet
this requirement in the respect that the component parts can be
made light in weight and manufacturing costs of the component
parts can be lowered .
It is to be understood that the form of the invention
herewith shown and described is to be taken as the preferred
embodiment of the same, and that various changes in the shape,
size and arrangement of parts may be resorted to without
departing from the spirit of the invention or the scope of the
subjoined claims.

Representative Drawing