GB1592420A

GB1592420A - Vibrator

Info

Publication number: GB1592420A
Application number: GB1614378A
Authority: GB
Original assignee: Okura Electric Industry Co Ltd
Current assignee: Okura Electric Industry Co Ltd
Priority date: 1978-04-24
Filing date: 1978-04-24
Publication date: 1981-07-08

Description

(54) VIBRATOR (71) We, OKURA ELECTRIC INDUSTRY Co., LTD., a Japanese company, of 10-7 4-chome, Shiroganedai Minato-ku, Tokyo, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a vibrator.

The well known vibrator hitherto used for conventional concrete placing work comprises an electric motor, namely a so called "double-headed motor", that has a motive shaft extending through the rotor to project to the front and rear of the motor. The vibrator including the motor is vibrated by means of an eccentric weight attached to each end of the projecting motive shaft. The number of rotations of the motor is ordinarily only 3000 rpm or so, and the number of rotations has to be increased to a value of up to 9000 rpm by the use of a separately provided frequency converter, generally called a "vibration amplifier". The motive shaft rotating at such a high speed inevitably exerts the turning impacts of the eccentric weights directly onto the bearings of the shaft, resulting in a decrease in the useful life of the bearings to only 2 to 3 months.

According to the present invention, there is provided a vibrator comprising a hollow motive shaft extending through a rotor of an electric motor to project to the front and rear of the motor; an unbalanced shaft for vibrating the vibrator, arranged in the hollow portion of the motive shaft in co-axial and non-integrally rotatable relationship to the motive shaft, and equipped with an eccentric weight at each end thereof; and a rotation transmitting means interposed between the motive shaft and the unbalanced shaft to transmit the rotation of the motive shaft to the unbalanced shaft in a manner such that both the shafts rotate in the same direction and the latter rotates more rapidly than the former.

The bearings of the vibrator of the invention undergo less vibration impacts than the bearings of a conventional vibrator at the same vibration amplitude, without the need for the frequency converter of high cost used in the conventional vibrator.

For a better understanding of the invention, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a fragmentary sectional view of a vibrator of the invention; Figure 2 is an elevational view of the front of the vibrator shown in Figure 1; Figure 3 is an elevational view of the eccentric weight of the vibrator shown in Figure 1; and Figure 4 is a fragmentary sectional view of another vibrator of the invention.

Referring to Figures 1 to 3, a three-phase A.C. motor 1 has a hollow motive shaft 2 extending through the rotor of the motor to project to the front and rear of the motor.

On each of the front and rear ends, an annular transmitting member 3 is fixed in co-axial relationship to the shaft 2 by a coupling key 4. (The member 3 on the rear end is not shown in Figure 1, since the elements denoted hereinafter by reference numerals 4 to 36 are in pairs, exclusive of part 18, disposed symmetrically on the front and rear, or right and left, sides of the centre line X of the vibrator, and the element at the rear are omitted). Screwed to the inner surface of the front end of the transmitting member 3, by a screw 6, is another annular member 5 onto the inner surface of which an annular toothed belt 7 with internal teeth is fixed by, for example, an adhesive.

The belt 7 may be made of a hard elastic material, such as a hard rubber or a synthetic rubber. An inscribed gear or pinion 8 engages the teeth 9 of the belt 7 so as to be rotatable by the rotation of the belt 7.

A flexible rotation-transmitting shaft 10 has one end fixed in a cylindrical body 11, the latter being fitted into hollow shaft 12 of the gear 8 and fixed thereto by a tapered pin 13. The shaft 12 of the gear 8 is held, by ball-bearings 14, in a carrying body 15 secured to the housing 17 of the vibrator by securing bolts 16. An unbalanced shaft 18 is arranged co-axially in a running fit in the hollow portion of the hollow motive shaft 2, by means of a ball-bearing 19, and an eccentric weight 20 is attached to the end of unbalanced shaft 18 by an annular mounting member 21 screwed onto the front end of the shaft and secured by a securing screw 22.

The eccentric weight 20 consists of a main body 23 and an eccentric adjustable plate 24 attached to the bod'y 23 in a justaposed relationship by a securing bolt 25 passing through, in a loose fit, an arc-shaped aperature 26 formed in the plate 24 and screwed into the main body 23. The plate 24 is mounted turnably on the annular mounting member 21 and is adapted to turn along the arc-shaped aperture 26. Thus, loosening of the bolt 25 and securing it again after suitable turning of the plate 24 enable one to adjust the eccentricity of the eccentric weight so that the desired vibration effect can be obtained. An aperture 27 is formed in the housing 17, and is used for enabling the plate 24 to be turned from the outside of the housing. A stopper flange 28 is provided on the bolt 25.

A coupling cylinder 29 is fixed onto the rear end of the flexible shaft 10. The base of the cylinder 29 is screwed into the screw portion 30 formed in the hollow portion of the unbalanced shaft 18 so that rotation of the shaft 10 causes rotation of the shaft 18.

Bolts 31 couple the vibrator to the body undergoing vibration (not shown). The vibrator has a ball-bearing 32 for the motive shaft 2, an oil plug 33 for the ball-bearings 14, ring packings 34 for oil, and 0 rings 35 and 36.

While, in the foregoing embodiment, the rotation-transmitting means between the motive shaft and the unbalanced shaft are disposed at both the front and rear of the motor, the vibrator may be so equipped only on the front or rear thereof, as shown in Figure 4. In Figure 4, the right hand portion of the vibrator has an identical construction to the right hand portion of the vibrator of Figure 1. The Figure shows a ball-bearing 32' for a motive shaft 2', a ball-bearing 19' for an unbalanced shaft 18', an eccentric weight 20', and an annular mounting member 21' for the eccentric weight. Elements 32', 19' and 20' may be the same as elements 32, 19 and 20 in Figure 1, while the front portions of the shafts 2' and 18' are the same as the front portions of the shafts 2 and 18 in Figure 1.

In operation, if the motive shaft 2 of the motor rotates as 3000 rpm, the flexible transmitting shaft 10 rotates at an increased speed of 9000 rpm by virtue of the transmission via the gear 8 and the belt 7. The unbalanced shaft 18, turning integrally with the shaft 10, rotates in the same direction as the shaft 2. This results in actuation of the eccentric weights 20 and causes vibration of the vibrator as a whole. Thus, the vibrator imparts the desired vibration to the object to be vibrated as it is secured to the object by the bolts 31.

As will be understood from the foregoing explanation, since the motive shaft 2 rotates at 3000 rpm while the unbalanced shaft 18 rotates at 9000 rpm in the same direction thereas, the bearing 19 is subjected to impacts equivalent to 6000 rpm (i.e. 9000 300C)) despite the fact that the shaft 18 rotates at 9000 rpm. In consequence, it will be evident that the bearings of the unbalanced shaft have the advantage of undergoing far less impacts due to the eccentric weights than do the bearings of a conventional vibrator, the latter bearings being directly subjected to impacts resulting from rotation of the motive shaft at 9000 rpm.

Thus, the useful life of the bearings of the vibrator of the invention is longer.

Furthermore, since the rotation of the motive shaft is transmitted to the unbalanced shaft by the annular belt having internal gear teeth, the inscribed gear engaging therewith and the flexible transmitting shaft, the unbalanced shaft and the motive shaft may rotate in the same direction such that the speed of the former is higher than that of the letter, without any transmission difficulties. It will be noted that other transmitting mechanisms, such as ordinary gear transmissions, would be very difficult to use in this case because of their complexity and because of their likelihood of damage due to vibration.

Since the vibrators shown in Figures 1 and 4 do not require the use of a frequency converter, they are less expensive.

WHAT WE CLAIM IS: 1. A vibrator comprising a hollow motive shaft extending through a rotor of an electric motor to project to the front and rear of the motor; an unbalanced shaft for vibrating the vibrator, arranged in the hollow portion of the motive shaft in coaxial and non-integrally rotatable relationship to the motive shaft, and equipped with an eccentric weight at each end thereof; and a rotation transmitting means interposed between the motive shaft and the unbalanced shaft to transmit the rotation of the motive shaft to the unbalanced shaft in a manner such that both the shafts rotate in the same direction and the latter rotates more rapidly than the former.

2. A vibrator as claimed in claim 1.

wherein the rotation transmitting means comprises an annular transmitting member fixed to one end of the motive shaft to rotate integrally and co-axially with the motive shaft; an annular belt having internal

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the hollow portion of the hollow motive shaft 2, by means of a ball-bearing 19, and an eccentric weight 20 is attached to the end of unbalanced shaft 18 by an annular mounting member 21 screwed onto the front end of the shaft and secured by a securing screw 22. The eccentric weight 20 consists of a main body 23 and an eccentric adjustable plate 24 attached to the bod'y 23 in a justaposed relationship by a securing bolt 25 passing through, in a loose fit, an arc-shaped aperature 26 formed in the plate 24 and screwed into the main body 23. The plate 24 is mounted turnably on the annular mounting member 21 and is adapted to turn along the arc-shaped aperture 26. Thus, loosening of the bolt 25 and securing it again after suitable turning of the plate 24 enable one to adjust the eccentricity of the eccentric weight so that the desired vibration effect can be obtained. An aperture 27 is formed in the housing 17, and is used for enabling the plate 24 to be turned from the outside of the housing. A stopper flange 28 is provided on the bolt 25. A coupling cylinder 29 is fixed onto the rear end of the flexible shaft 10. The base of the cylinder 29 is screwed into the screw portion 30 formed in the hollow portion of the unbalanced shaft 18 so that rotation of the shaft 10 causes rotation of the shaft 18. Bolts 31 couple the vibrator to the body undergoing vibration (not shown). The vibrator has a ball-bearing 32 for the motive shaft 2, an oil plug 33 for the ball-bearings 14, ring packings 34 for oil, and 0 rings 35 and 36. While, in the foregoing embodiment, the rotation-transmitting means between the motive shaft and the unbalanced shaft are disposed at both the front and rear of the motor, the vibrator may be so equipped only on the front or rear thereof, as shown in Figure 4. In Figure 4, the right hand portion of the vibrator has an identical construction to the right hand portion of the vibrator of Figure 1. The Figure shows a ball-bearing 32' for a motive shaft 2', a ball-bearing 19' for an unbalanced shaft 18', an eccentric weight 20', and an annular mounting member 21' for the eccentric weight. Elements 32', 19' and 20' may be the same as elements 32, 19 and 20 in Figure 1, while the front portions of the shafts 2' and 18' are the same as the front portions of the shafts 2 and 18 in Figure 1. In operation, if the motive shaft 2 of the motor rotates as 3000 rpm, the flexible transmitting shaft 10 rotates at an increased speed of 9000 rpm by virtue of the transmission via the gear 8 and the belt 7. The unbalanced shaft 18, turning integrally with the shaft 10, rotates in the same direction as the shaft 2. This results in actuation of the eccentric weights 20 and causes vibration of the vibrator as a whole. Thus, the vibrator imparts the desired vibration to the object to be vibrated as it is secured to the object by the bolts 31. As will be understood from the foregoing explanation, since the motive shaft 2 rotates at 3000 rpm while the unbalanced shaft 18 rotates at 9000 rpm in the same direction thereas, the bearing 19 is subjected to impacts equivalent to 6000 rpm (i.e. 9000 300C)) despite the fact that the shaft 18 rotates at 9000 rpm. In consequence, it will be evident that the bearings of the unbalanced shaft have the advantage of undergoing far less impacts due to the eccentric weights than do the bearings of a conventional vibrator, the latter bearings being directly subjected to impacts resulting from rotation of the motive shaft at 9000 rpm. Thus, the useful life of the bearings of the vibrator of the invention is longer. Furthermore, since the rotation of the motive shaft is transmitted to the unbalanced shaft by the annular belt having internal gear teeth, the inscribed gear engaging therewith and the flexible transmitting shaft, the unbalanced shaft and the motive shaft may rotate in the same direction such that the speed of the former is higher than that of the letter, without any transmission difficulties. It will be noted that other transmitting mechanisms, such as ordinary gear transmissions, would be very difficult to use in this case because of their complexity and because of their likelihood of damage due to vibration. Since the vibrators shown in Figures 1 and 4 do not require the use of a frequency converter, they are less expensive. WHAT WE CLAIM IS:

1. A vibrator comprising a hollow motive shaft extending through a rotor of an electric motor to project to the front and rear of the motor; an unbalanced shaft for vibrating the vibrator, arranged in the hollow portion of the motive shaft in coaxial and non-integrally rotatable relationship to the motive shaft, and equipped with an eccentric weight at each end thereof; and a rotation transmitting means interposed between the motive shaft and the unbalanced shaft to transmit the rotation of the motive shaft to the unbalanced shaft in a manner such that both the shafts rotate in the same direction and the latter rotates more rapidly than the former.

2. A vibrator as claimed in claim 1.

gear teeth, fixed to the inner surface of the annular transmitting member; an inscribed gear engaging the annular belt so as to be rotatable by the rotation of the annular belt; and a flexible rotation-transmitting shaft for transmitting the rotation of the inscribed gear to the unbalanced shaft.

3. A vibrator as claimed in claim 1, wherein the rotation transmitting means comprises an annular transmitting member fixed to each end of the motive shaft to rotate integrally and co-axially with the motive shaft; an annular belt having internal gear teeth, fixed to the inner surface of each of the annular transmitting members; an inscribed gear engaging each annular belt so as to be rotatable by the rotation of the respective annular belt, and a flexible rotation-transmitting shaft for transmitting the rotation of each inscribed gear to the unbalanced shaft.

4. A vibrator as claimed in claim 2 or 3, wherein the or each annular belt is made of an elastic, hard material.

5. A vibrator substantially as hereinbefore described with reference to Figure 1 to 3 or Figure 4 of the accompanying drawings.