GB2103333A - Improvements in vibrators - Google Patents

Abstract

A vibrator comprises a table 1 supported above a sub frame 2 by resilient mounts 3. The table 1 is vibrated by rotating bodies 13 and 18 vibrations being transmitted through inflatable chambers 8, the air pressure in which is adjustable to determine the stiffness of the transmission. Applicable to apparatus for moulding slurries. <IMAGE>

Description

SPECIFICATION Improvements in vibrators This invention relates to a machine for causing an article to vibrate, such machine being herein referred to as a vibrator. A vibrator in accordance with the invention finds particular application in the moulding of slurries, where vibration may be required to cause even distribution of a slurry in a mould.

Avibrator has been proposed which comprises a resiliently flexibly mounted table and a motor fixed to the table, said motor being adapted to drive a body to rotate about an axis spaced from the centre of gravity of the body. On a vibrator of this type the provisions for altering the amplitude of vibration are: altering the mass of the driven body, altering the disposition of the mass of the body about the axis of its rotation, and altering the speed of rotation of the motor.

The first two methods are unsatisfactory primarily because it is difficult to effect an adjustment to the vibration amplitude of a vibrator employing these methods while the vibrator is in operation. The third method is unsuitable for vibrators used in the moulding of slurries because for a vibrator to be effective to this application the frequency of vibration must remain substantially constant between the limits of 25-200 Hz.

According to the present invention there is provided a vibrator of the kind set forth above wherein the motor is connected to the table by a member whose stiffness is adjustable, the selected degree of stiffness determining the amplitude of the vibrations transmitted to the table.

In an embodiment the said member is an inflatable chamber having flexible walls. The resilience of such a member is determined by regulating the fluid pressure inside it.

A particular embodiment of the present invention will now be described with reference to the following informal drawings wherein: Figure 1 is a side view of a vibrator in accordance with the present invention.

Figure 2 is a section through A.A' in Figure 1.

Referring to both Figures 1 and 2, the vibrator illustrated comprises a table 1 supported above a subframe 2 by resilient amounts 3. The subframe 2 comprises a base 4, which is generally rectangular in plan, guide posts 5 and support pillars 6, the guide posts 5 and the support pillars 6 extending vertically upwardly from the base 4. The resilient mounts 3 bear on the tops of support pillars 6. Electric motors 9, mounted between brackets 10 and 11 are suspended below the table 1 in a cradle 7 (not shown in Figure 2), and held between the lower part of the cradle 7 and the table 1 by a plurality of inflatable chambers 8 and 12. Chambers 8 lie between lower bracket 10 and the lower part of cradle 7, and chambers 12 lie between upper bracket 11 and the table 1.Bodies 13 and 18 are fixed to the motor output shafts 14, in such a way that the axes of shafts 14 do not pass through the centres of gravity of the bodies 13 and 18 to which the shafts 14 are fixed.

The vertical guide posts 5 pass through holes 15 in the table 1 and through collars 16 which are fixed, around holes 15, to the underside of table 1. The subframe 2 is conveniently mounted on blocks 17.

In use the bodies 13 and 18 are rotated about the shafts 14 by the motors 9 and the motors 9 are caused to vibrate. The bodies 13 are rotated in the opposite direction to bodies 18 and, are synchronised so that the resulting vibration is only in the vertical direction. The amount of the said vibration which is transmitted to the table 1 is determined by the stiffness of the inflatable chambers 8 and 12.

Thus the amount of vibration transmitted to the table increases with an increase in the air pressure in the chambers 8 and 12 and decreases with a decrease in the air pressure in chambers 8 and 12.

1. A vibrator comprising a resiliently flexibly mounted table and a motor connected to the table by a member of adjustable stiffness, the motor being adapted to drive a body to rotate about an axis spaced from the centre of gravity of the body.

2. A vibrator as claimed in claim 1 wherein the said member is an inflatable chamber having flexible walls.

3. A vibrator substantially as herein described with reference to the accompanying drawings.

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

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in vibrators This invention relates to a machine for causing an article to vibrate, such machine being herein referred to as a vibrator. A vibrator in accordance with the invention finds particular application in the moulding of slurries, where vibration may be required to cause even distribution of a slurry in a mould. Avibrator has been proposed which comprises a resiliently flexibly mounted table and a motor fixed to the table, said motor being adapted to drive a body to rotate about an axis spaced from the centre of gravity of the body. On a vibrator of this type the provisions for altering the amplitude of vibration are: altering the mass of the driven body, altering the disposition of the mass of the body about the axis of its rotation, and altering the speed of rotation of the motor. The first two methods are unsatisfactory primarily because it is difficult to effect an adjustment to the vibration amplitude of a vibrator employing these methods while the vibrator is in operation. The third method is unsuitable for vibrators used in the moulding of slurries because for a vibrator to be effective to this application the frequency of vibration must remain substantially constant between the limits of 25-200 Hz. According to the present invention there is provided a vibrator of the kind set forth above wherein the motor is connected to the table by a member whose stiffness is adjustable, the selected degree of stiffness determining the amplitude of the vibrations transmitted to the table. In an embodiment the said member is an inflatable chamber having flexible walls. The resilience of such a member is determined by regulating the fluid pressure inside it. A particular embodiment of the present invention will now be described with reference to the following informal drawings wherein: Figure 1 is a side view of a vibrator in accordance with the present invention. Figure 2 is a section through A.A' in Figure 1. Referring to both Figures 1 and 2, the vibrator illustrated comprises a table 1 supported above a subframe 2 by resilient amounts 3. The subframe 2 comprises a base 4, which is generally rectangular in plan, guide posts 5 and support pillars 6, the guide posts 5 and the support pillars 6 extending vertically upwardly from the base 4. The resilient mounts 3 bear on the tops of support pillars 6. Electric motors 9, mounted between brackets 10 and 11 are suspended below the table 1 in a cradle 7 (not shown in Figure 2), and held between the lower part of the cradle 7 and the table 1 by a plurality of inflatable chambers 8 and 12. Chambers 8 lie between lower bracket 10 and the lower part of cradle 7, and chambers 12 lie between upper bracket 11 and the table 1.Bodies 13 and 18 are fixed to the motor output shafts 14, in such a way that the axes of shafts 14 do not pass through the centres of gravity of the bodies 13 and 18 to which the shafts 14 are fixed. The vertical guide posts 5 pass through holes 15 in the table 1 and through collars 16 which are fixed, around holes 15, to the underside of table 1. The subframe 2 is conveniently mounted on blocks 17. In use the bodies 13 and 18 are rotated about the shafts 14 by the motors 9 and the motors 9 are caused to vibrate. The bodies 13 are rotated in the opposite direction to bodies 18 and, are synchronised so that the resulting vibration is only in the vertical direction. The amount of the said vibration which is transmitted to the table 1 is determined by the stiffness of the inflatable chambers 8 and 12. Thus the amount of vibration transmitted to the table increases with an increase in the air pressure in the chambers 8 and 12 and decreases with a decrease in the air pressure in chambers 8 and 12. CLAIMS

1. A vibrator comprising a resiliently flexibly mounted table and a motor connected to the table by a member of adjustable stiffness, the motor being adapted to drive a body to rotate about an axis spaced from the centre of gravity of the body.

2. A vibrator as claimed in claim 1 wherein the said member is an inflatable chamber having flexible walls.

3. A vibrator substantially as herein described with reference to the accompanying drawings.