Machine element or mechanism – Mechanical movements – Reciprocating or oscillating to or from alternating rotary
Reexamination Certificate
2001-11-09
2004-11-16
Schwartz, Christopher P. (Department: 3683)
Machine element or mechanism
Mechanical movements
Reciprocating or oscillating to or from alternating rotary
Reexamination Certificate
active
06817260
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a ball screw with cooling means and more particularly, a ball screw with high efficiency cooling means.
2. Description of the Prior Art
FIG. 1
shows cooling means for a conventional ball screw. As shown in
FIG. 1
, a tunnel like through pathway
11
is bored penetrating along the longitudinal direction of a screw bolt
10
so as to provide a path for a cooling liquid thereby carrying away the heat of the screw bolt
10
imparted by the screw nut
12
and the circulating steel balls. It is well known to men skilled in the art that the operating principle of a ball screw and nut assembly is the screw nut
12
engaging a work piece or a working platform moves along the lengthwise direction of the screw bolt
10
by spirally rotation of the screw nut
12
with respect to the screw bolt
10
. The screw nut
12
is coaxially sleeving over the screw bolt
10
and both structures are coupled with two threaded grooves each formed on the inner surface of the screw nut
12
and the outer surface of the screw bolt
10
respectively with a plurality of rolling balls interposed therebetween. By so the work piece or the working platform is able to perform its work by moving along the lengthwise direction of the screw bolt
10
. In fact, owing to the fact that it is the screw nut
12
that actually carries the load of the work piece or the working platform and always in contact with the rolling balls so that its heat dissipation is difficult. On the contrary, the screw bolt
10
is constructed far longer than the screw nut
12
so that a major part of it is exposed to the air with a good air cool effect. Therefore, to form a cooling agent path along the lengthwise direction of the screw bolt
10
for heat dissipation as that has been commonly practiced in conventional techniques is definitely nonsense as putting the cart before the horse. Besides, forming a through pathway
11
coaxially along the longitudinal direction in a slim screw bolt
10
accurately requires a very fine technique to perform, a slight inadvertent alignment of center position may cause vibration of the screw bolt
10
during operation, or to the worst, result in cracking of the screw bolt
10
.
SUMMARY OF THE INVENTION
In view of the foregoing situation, the inventor of the present invention herein conducted intensive research based on many years of experience gained through professional engagement in the manufacturing of related products, with continuous experimentation and improvement culminating in the development of efficient cooling means for ball screw of the invention herein.
Instead of boring a longitudinal through pathway for cooling agent along the screw bolt situated at better cooling condition, a cavity is formed between an outer cover and the screw nut as a pathway for cooling agent so as to deprive the screw nut of heat generated therein. Leak proof means such as several O rings are provided between the outer cover and the screw nut to prevent the cooling agent from leaking out of the cavity. To assure a better cooling effect, portion of the wall of the screw nut adjacent to the outer cover is pared partially in planar or curved surface to enlarge the space of the cavity and reduce the wall thickness of the screw nut thereby improving the cooling effect. Furthermore, a guiding tube spirally encircling the screw nut, or reciprocating in the longitudinal direction of the ball screw axis on the screw nut, is provided for guiding the cooling agent therein so as to prevent leaking of cooling agent.
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patent: 5749266 (1998-05-01), Tsukada
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Dennison Schultz Dougherty & MacDonald
Hiwin Technologies Corporation
Schwartz Christopher P.
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