The invention relates to a clamping device for connection in which a worm screw is brought into mesh with an array of teeth portion defined on a strap band so as to diametrically contract it upon tightening the strap band around a connecting portion.
This type of the clamping device has been disclosed by Japanese Utitily Model Publication No. 6-23822, Japanese Laid-open Patent Application No. 61-244906 and Japanese Patent Publication No. 7-26711 (referred to as “first document”,“second document” and “third document” in turn hereinafter).
In the first document, a portion in which slantwise grooves are defined to make a worm screw mesh with the grooves, is swollen in the diametrical direction to distance from a hose-forming section so as to prevent an incidental damage on the hose. This prevents a maximum surface pressure from exerting at the contact portion between a band and the hose, so as for the band not to stick into the slantwise grooves due to the action of the screw worm.
In the second document, it is taken into consideration that an increased width of gear grooves tends to tear an outer band upon tightening the band when the gear grooves are formed by means of a punching procedure. Instead of the punching procedure, a drawing and extrusion method (half-cut procedure) are used as an example of forging procedure to form the gear grooves. This enlarges a contact area in which a worm screw gets meshed with the gear grooves so as not to easily tear the band when tightened with an increased torque.
In the third document, the document discloses a bias structure as an elastic accumulation device which gives an urging force to a strap by means of multiple types of spring. With the use of these springs, the structure makes up for a tightening force by an amount reduced after the strap is tightened so as to minimize the reduced amount of the tightening force of the strap.
In the structure where the slantwise grooves are swollen as disclosed in the first document, the structure increases a bending rigidity of the band in its circumferential direction. Under the above structure, it becomes necessary to apply a larger amount of tightening force to the band so as to increase a sliding pressure of the worm screw against the slantwise grooves, thus producing a possibility to do damage on the screw worm and the slantwise grooves so as to lose the normal function of the band.
A housing in the first document seems to be secured to the band by bending a lower end portion of the housing as judged in the manner depicted by Figures attached to the first document. For this reason, the housing is subjected to a reactionary force via the worm screw from the band upon tightening the worm screw, thus deforming the lower end portion of the housing to extend in the diametrical direction. This decreases a meshing allowance of the worm screw against the slantwise grooves, thus increasing the sliding pressure between the worm screw against the slantwise grooves so as to aggravate the above inconvenience.
A meshing allowance of the worm gear against the gear grooves in the second document is due to the valley portions of the worm gear and the linear convex portions of the outer band. The structure permits the outer band to compensate the bending rigidity by an amount which would be lost when the grooves are perforated through, while at the same time, increasing the reactionary force, to which the worm gear is subjected through the band.
For this reason, a large amount of the reactionary force increases the sliding pressure of the worm gear against the gear grooves to do damage on the gear grooves or excessively wear the valley portion of the worm gear so as to bring it out of mesh especially when tightly winding the band.
The third document shows that a strap is tightened against a rubber hose by the force of approx. 10-30 kg/cm2 with the compressibility of the rubber hose as approx. 20-30%. This is effective in compensating the tightening force of the band by an amount in which the rubber hose contracts although it raises a manufacturing cost due to an increased number of component parts with a complicated structure.
Judging from the manner as depicted in
Judging from the housing partly notched in the second document, the lower end portion of the housing is seemingly bent against an inner side of the strap. This produces a deforming force on the housing to disengage the screw bolt out of the teeth portion due to the larger amount of the reactionary force, to which the housing is subjected through the strap when tightly winding the strap around the connecting portion.
In any of the documents mentioned above, it is not sufficient to cope with the above inconveniences especially when tightening the strap with the increased torque.
Therefore, it is an object of the invention to overcome the above drawbacks, and provide a clamping device for connection which is capable of increasing a contact area between a worm screw and an array of teeth portion, while decreasing a sliding pressure per a unit area therebetween, thus maintaining a good meshing condition between the worm screw and the array of teeth portion for an extended period of time when tightening a strap band with an increased torque.
According to the invention, there is provided a clamping device for connection in which a strap band formed into an open-end annular configuration so as to be tightly wound around a connecting portion to be connected. A housing is fixed to one end portion of the strap band in its circumferential direction with a worm screw rotatably accommodated into the housing. An array of teeth portion is arranged on the other end of the strap band so that the teeth portion comes to mesh with the worm screw within the housing, so as to tighten the strap band against the connecting portion by rotating the worm screw against the array of teeth portion. The other end portion of the strap band in which the array of teeth portion resides, is formed into a wavy and concavo-convex configuration in a width direction of the strap band, so as to increase a meshing area of the array of teeth portion against the worm screw.
With the array of teeth portion formed into the wavy and concavo-convex configuration in the width direction, it is possible to increase a contact area or sliding pressure between the worm screw and the array of teeth portion. While at the same time, the array of teeth portion increases its bending rigidity to improve the physical strength in the direction in which the array of the teeth portion is subjected to the sliding pressure from the worm screw.
This makes it possible to mesh the array of teeth portion of high bending rigidity with the worm screw through an enlarged contact area, thus spreading the sliding pressure of the worm screw against the array of teeth portion so as to decrease the sliding pressure per a unit area. As a result, it becomes possible to maintain a good meshing condition between the worm screw and the array of teeth portion for an extended period of time without doing damage on the worm screw and the teeth portion upon tightly meshing the worm screw with the array of the teeth portion.
With the improved bending rigidity and the enlarged contact area between the worm screw and the teeth portion, it is possible for the array of the teeth portion to resist against an increased sliding pressure transmitted from the worm screw so as to cope with the situation in which the worm screw is tightly meshed with the array of the teeth portion. This is inexpensively done by only providing the wavy and concavo-convex configuration on the strap band on which the array of teeth portion is defined.
According to other aspect of the invention, the strap band is made of an elastic material, and having a plurality of segments raised up intermittently in the circumferential direction. Each end of the segments is oriented opposite to a direction in which the strap band slides over the connecting portion upon tightening the strap band to make it wind around the connecting portion. With each end of the segments oriented opposite to the direction in which the strap band slides over the connecting portion, it is possible to prevent the segments from sticking against an outer surface of the connecting portion.
In the case in which the strap band is tightened around the connecting portion through a rubber hose, the tightened rubber hose weakens its restitutive force and lessens the tightening force against the connecting portion after tightening the strap band because the rubber hose has an elastic aftereffect due to its viscoelastic property.
Due to the reason that each end of the segments is oriented opposite to the direction in which the strap band slides over the connecting portion, it is possible for the segments to push against the rubber hose by an amount in which the rubber hose is viscoelastically contracted so as to compensate the tightening force lost in the strap band. This is particularly advantageous when the strap band substantially loses its tightening force against the connecting portion with a higher compressibility ratio observed on the rubber hose upon tightly winding the strap band around the connecting portion.
According to other aspect of the invention, the worm screw is formed by means of a rolling procedure, and the housing has an enveloping portion to surround the array of teeth portion. The enveloping portion is ironed out to reduce a thickness of the enveloping portion.
The enveloping portion is differentiated in thickness than other portion of the housing so as to improve the bending rigidity, in addition the worm screw being rolled to produce a high bending rigidity.
For this reason, it is possible to minimize the tendency in which the worm screw disengages out of the array of teeth portion with the housing retained as the original shape when the housing is subjected to a larger reactionary force through the worm screw. From this point of view, it is possible to maintain a good meshing condition between the worm screw and the array of teeth portion for an extended period of time.
According to other aspect of the invention, the housing has a streak of convex reinforcement on a flat surface provided with the housing. This increases the bending rigidity of the housing to obtain the same advantages as mentioned above.
According to other aspect of the invention, the array of teeth portion consists of narrow slits defined on the strap band. Due to the array of teeth portion being narrow slits, it is possible to manufacture the array of teeth portion with a combination of punching and bending procedures, thus making the manufacturing the teeth portion advantageously in terms of cost.
According to other aspect of, the invention, the worm screw has a screw pitch surface defined into a hyperboloidal configuration so as to increase a meshing area against the array of teeth portion. This substantially spreads the sliding pressure of the worm screw against the array of teeth portion to decrease the sliding pressure per a unit area. For this reason, it is possible to maintain a good meshing condition between the worm screw and the array of teeth portion, and well-suited to a clamping device which requires a larger tightening force applied to the connecting portion.
Preferred forms of the present invention are illustrated in the accompanying drawings in which:
In the following description of the depicted embodiments, the same reference numerals are used for features of the same type.
Referring to
One end portion 3A of the strap band 3 is surrounded by the connection lugs 4a, 4b, butted ends 4A of which are bonded by means of TIG welding procedure or the like. One end portion 3A of the strap band 3 is secured to the connection lugs 4a, 4b by means of a spot welding, projection welding or the like. The other end portion 3B of the strap band 3 is placed in the housing 4 to overlap with the one end portion 3A of the strap band 3.
The strap band 3 has an arcuate portion 3a which defines a plurality of slit teeth portion 6 at regular intervals as an array of teeth portion in the circumferential direction. As shown in
In this instance, the worm screw 5 has ridge portions 4s at a predetermined lead pitch as shown in
The one end portion 3A of the strap band 3 may be shaped into wavy or arcuate form in the width direction in order to support the slit teeth portion 6 as shown in
With the structure thus described, as shown at an arrow A in
With the slit teeth portion 6 formed into the wavy and concavo-convex configuration in the width direction, it is possible to increase a contact area or sliding pressure between the worm screw 5 and the slit teeth portion 6. While at the same time, the slit teeth portion 6 increases its bending rigidity to improve the physical strength in the direction in which the slit teeth portion 6 is subjected to the sliding pressure from the worm screw 5.
This makes it possible to mesh the slit teeth portion 6 of high bending rigidity with the worm screw 5 through an enlarged contact area, thus spreading the sliding pressure of the worm screw 5 against the slit teeth portion 6 so as to decrease the sliding pressure per a unit area. As a result, it becomes possible to maintain a good meshing condition between the worm screw 5 and the slit teeth portion 6 for an extended period of time without doing damage on the worm screw 5 and the slit teeth portion 6 especially when tightly meshing the worm screw 5 with the slit teeth portion 6.
With the improved bending rigidity and the enlarged contact area between the worm screw 5 and the slit teeth portion 6, it is possible for the slit teeth portion 6 to resist against an increased sliding pressure transmitted from the worm screw 5 so as to cope with the situation in which the worm screw 5 is tightly meshed with the slit teeth portion 6.
As the case in which a larger amount of tightening force is required for the connecting portion 2, an example is taken when connecting an intercooler to an intake pipe in an internal combustion engine equipped with a supercharger or turbocharger (each not shown). The intercooler is provided to cool a compressed air in order to increase the pneumatic stowing ratio. The turbocharger feeds the compressed air to an intake port (not shown) through the intercooler and the intake pipe.
The structure is such that a larger amount of air pressure is applied to the connecting portion between the intercooler and the intake pipe. This requires the strap band to apply a larger tightening force substantially equivalent to the pressure of the compressed air.
In the present invention, the ratio (A P/A D) of the surface pressure P to the tightening amount D is greater than that of the prior counterpart as understood by comparing the diamond legends (prior counterpart) and the triangular legends (subject invention) in
Since the sufficient tightening torque T and surface pressure P are achieved with a relatively small tightening amount D, it is possible to attach the strap band 3 to the connecting portion 2 for a short period of time so as to improve the working efficiency. It is to be noted that the worm screw 5 and the slit teeth portion 6 were lubricated before obtaining the graphical representations in
In the prior counterpart as shown in
Contrary to the prior counterpart, with the slit teeth portion 6 formed into the wavy and concavo-convex configuration, it is possible in the subject invention for the strap band 3 to eliminate the necessity of providing any means corresponding to the opening portion 3H, thus enabling the strap band 3 to insure an appropriate physical strength.
With the thickness of the connection lugs 4a, 4b thus reduced, it is also possible to regulate an advancement of the connection lugs 4a, 4b in their thickness direction. This makes it possible to make the connection lugs 4a, 4b substantially in flush with an inner surface of the strap band 3 even if the bulged degree of the bulged portion 3C is limited to a certain extent. As a result, this enables the strap band 3 to generally maintain a uniform distribution of the surface pressure exerting against the connecting portion 2.
With each end of the segments 8 oriented opposite to the direction C in which the strap band 3 slides over the connecting portion 2, it is possible to prevent the segments 8 from sticking against an outer surface of the connecting portion 2.
In the case in which the strap band 3 is tightened around the connecting portion 2 through a rubber hose (not shown), the tightened rubber hose weakens its restitutive force and lessens the tightening force against the connecting portion 2 after tightening the strap band 3 because the rubber hose has an elastic aftereffect due to its viscoelastic property.
By way of illustration, if the strap band 3 is tightened around the rubber hose with the magnitude of 40 kg/cm2, a compressibility ratio observed on the rubber hose becomes approx. 30%. After tightening the strap band 3 around the rubber hose, it is found that the tightening force reduces to 30 kg/cm2.
Due to the reason that each end of the segments 8 is oriented opposite to the direction C in which the strap band 3 slides over the connecting portion 2, it is possible for the segments 8 to push against the rubber house by an amount in which the rubber hose is viscoelastically contracted so as to compensate the tightening force lost in the strap band 3.
As is the case with connecting an inter cooler and an intake pipe, this is particularly advantageous when the strap band 3 substantially loses its tightening force against the connecting portion 2 with a higher compressibility ratio observed on the rubber hose upon tightly winding the strap band 3 around the connecting portion 2.
Examples of the segments represented herein are as shown in
With the screw pitch surface defined into a hyperboloidal configuration, it is possible to substantially spreads the sliding pressure of the worm screw 9 against the slit teeth portion 6 to decrease the sliding pressure per a unit area. For this reason, it is possible to maintain the good meshing condition between the worm screw 9 and the slit teeth portion 6.
This is particularly advantageous when a diameter of the connecting portion 2 is relatively small because it is possible to remarkably increase the meshing number of worm screw 9 against the slit teeth portion 6 so as to render the above good meshing condition better between the worm screw 9 and the slit teeth portion 6.
(a) It is to be noted that reinforced synthetics, copper plate or alloyed metal may be used to the strap band 3 instead of the stainless steel (SUS304).
(b) Discrete tongue plates may be welded to the strap band 3 instead of the raised-up segments 8.
(c) Instead of the wavy and concavo-convex configuration, the arcuate portion 6 of the strap band 3 may be sharply formed into an M-shaped or W-shaped configuration as long as it increases the sliding and meshing area of the slit teeth portion 6 against the worm screw 5, 9.
(d) In order to smoothly operate the worm screw 5, 9 rotationally, lubricants (e.g., MoS2, grease, polyfluoroethylene) may be applied between the worm screw 5, 9, and the slit teeth portion 6.
(e) At least either of the worm screw 5, 9 or the slit teeth portion 6 may be processed with a surface treatment such as a tin-plating, diamond-like carbon (DLC), salt bath (TD), ionized nitriding, TiC film or TiCN film.
In a clamping device for connection in which a worm screw is rotationally operated through an array of teeth portion to tighten a strap band, the array of teeth portion is formed into a wavy and concavo-convex configuration in the width direction, it is possible to increase a contact area or sliding pressure between the worm screw and the array of teeth portion. While at the same time, the array of teeth portion increases its bending rigidity to improve the physical strength in the direction in which the array of the teeth portion is subjected to the sliding pressure from the worm screw. This makes it possible to mesh the teeth portion of high bending rigidity with the worm screw through an enlarged contact area. It becomes possible to maintain a good meshing condition between the worm screw and the array of teeth portion upon tightly meshing the worm screw with the array of the teeth portion. In the case in which a larger amount of tightening force is required for the connecting portion, as connecting an intercooler (for cooling the compressed air) to an intake pipe in an internal combustion engine equipped with a supercharger or turbocharger, it is well-suited to a clamping device which requires a larger tightening force applied to the connecting portion and resultantly exhibits sufficient utility in the mechanical industry.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP04/05225 | 4/12/2004 | WO | 6/7/2007 |