Bearings – Linear bearing – Recirculating
Reexamination Certificate
2001-05-18
2003-05-06
Hannon, Thomas R. (Department: 3682)
Bearings
Linear bearing
Recirculating
Reexamination Certificate
active
06558039
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a linear guide way and, more particularly, to a linear guide way in which a slide block is installed without using any screws with the result that a preferable improvement can be expected for the structure of a smaller sized linear guide way.
2. Description of the Prior Art
FIG. 6
shows a conventional linear guide way. As shown in
FIG. 6
, the conventional linear guide way comprises a rail
1
, a sliding block
2
, two end caps
3
, two guide plates
4
, and two oil scrapers. The end caps
3
, the guide plates
4
, and the oil scrapers
5
are engaged to the sliding block
2
with screws
6
. Several attachment holes
12
and several screw holes
22
are respectively formed on the rail
1
and the sliding block
2
. The attachment holes
12
are used to fix the rail
1
on the main structure. On the other hand, the screw holes
22
are used for assembling the slide block
2
with the structure. As the size of the sliding block
2
becomes smaller, the size of the screws
6
becomes smaller accordingly. When the size of the screws
6
is minimized to a certain degree, the manufacturing of the screws
6
becomes more difficult. As a result, utilizing the screws for assembling a linear guide way as shown in
FIG. 6
is difficult and unable to pay in case of constructing a tiny linear guide way.
FIG. 7
shows a schematic view of a recently patented structure for a linear guide way (U.S. Pat. No. 6,042,269). In this invention the guide plates
4
and the sliding block
2
are fixedly conjoined together by ejection process. Two stop pins
31
are provided for each end cap
3
. On the other hand, two insertion holes
41
are formed for each guide plate
4
. When assembling the end cap
3
with the guide plates
4
, the stop pin
31
is inserted into the insertion hole
41
and engaged with each other. The innovative improvement was made such that the stop pin
31
has an enlarged pin head
311
, while an aperture
42
is formed on each side of the guide plate
4
. When separating the end cap
3
and the guide plate
4
, the pin head
311
is previously pressed to shrink by inserting a tool from the aperture
42
so as to facilitate extraction of the stop pin
31
and separation of end cap
3
and the guide plate
4
. With this structure, the embarrassing problem in utilization of screws in a small sized linear guide way is overcome, and the production cost is reduced. However, there arises four new problems. First, after having been completed grinding process, the sliding block
2
has to go through a forming process by ejection under temperature of 150~200° C. that reaches the annealed temperature of steel material very likely to cause change of metallic phase and material deformation. As a result, a final finishing accuracy of the product will be degraded. Second, during ejection process for forming the guide plate
4
and the sliding block
2
in an integral piece. It is well known that the thermal expansion coefficient of plastic for forming the guide plate
4
, is approximately(7~10)×10
−5
, while that of alloy steel for forming the sliding block
2
is approximately 1×10
−5
. The difference between the two ranges is as large as to 7~10 times. Disintegration between plastic and steel will definitely occur not long after operation owing to repeated thermal stress resulting in unrepairable failure of the linear guide way. Third, the allowable necessary clearance existing between the stop pin
31
and both end caps
3
and guide plates
4
will exacerbate loosening of engagement between the end cap
3
and the guide plate
4
by constant impact of circulating steel balls against the end cap
3
when the sliding block
2
is moving fast. Fourth, although the aperture
42
is provided for facilitating extraction of the stop pin
31
, an extra tool is required.
SUMMARY OF THE INVENTION
The present invention has thus been made in order to eliminate the inconvience inherent to the two conventional techniques as mentioned above.
In the present invention, spring strips are employed for engaging the end cap and the sliding block instead of screws and pins. As a matter of fact, the loading force of the screws in a linear guide way is not great. The force of the end caps which depends on the screws to support is an impact force exerted by steel balls turning their direction during circulation and is nothing to do directly with the load of the linear guide way. Actually, the force which the end caps have to withstand is influenced by the force generated from moving speed of the sliding block in the linear guide way, but this force is quite small compared to the load of the linear guide way. The resilient force of spring strips is enough to cope with this force for engaging the end caps with the sliding block instead of using screws.
It is a common sense that deformation of a spring affects its resiliency, but a minor deformation will by no means cause a severe fatigue of elasticity, which greatly reduces the resilient force of a spring. Therefore, the end caps and the sliding block can be reliably combined together without the fear of loosening during the life span.
In the present invention, the plastic end caps are attached to the metallic slide block with a constant spring force without employing any binding means so that the problem of exfoliation between metallic part and plastic part never occurs as that is always experienced in conventional techniques. Moreover, a tedious ejection process for combining the plastic end caps with the metallic slide block as that must be carried out in the cited case (U.S. Pat. No. 6,042,269) is eliminated thereby further evading the problem of disintegration of the two parts due to thermal stress as mentioned above.
In the present invention, a gripping angle and a guiding angle are formed at each side of the spring strip into gripping fissure formed in the end cap so as to forcibly conjoin the end cap with the sliding block. With such means of conjoining the end cap and the sliding block by the spring force employed in the present invention has solved the problem of difficulty in extracting the stop pin, and this problem has been embarrassing the aforesaid cited case. The spring strip of the present invention can be easily dug up with a common screw driver in case of detaching the end cap from the sliding block.
In the present invention, the metallic spring strip whose mechanical strength is far greater than that of plastic material is used to conjoin the end cap with the sliding block and is embraceably mounted at the position where being susceptible to structural deformation due to material deterioration and abrupt variation of environmental condition such as temperature and moisture so as to minimize rate of failure of the linear guide way.
REFERENCES:
patent: 4974971 (1990-12-01), Tanaka
patent: 5102235 (1992-04-01), Mugglestone
patent: 5265963 (1993-11-01), Kawaguchi
patent: 5295748 (1994-03-01), Yamazaki
patent: 5340219 (1994-08-01), Agari
patent: 5435649 (1995-07-01), Kuwahara
patent: 6106154 (2000-08-01), Agari
patent: 6170986 (2001-01-01), Hsu et al.
patent: 6200031 (2001-03-01), Faulhaber et al.
patent: 6210040 (2001-04-01), Mischler
Bacon & Thomas PLLC
Hannon Thomas R.
Hiwin Technologies Corp.
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