GB2099115A - Antivibration mounting for machinery - Google Patents

Abstract

An antivibration mounting for motors, pumps, winches and the like machinery is formed on an inclined or level supporting structure by casting one or more pads by displacing a body of resin-based material into a space defined between a machine base plate 1 and a support 2 by a U-shaped forming piece 5 located within a porous part 7 of a bag 6, the bag 6 also having a non porous end from which the resin material is displaced, e.g. by rolling the bag up from the end on a roller 13. A shim or plate such as 8 may be placed between the base 1 and the bag 6, and a similar shim or plate between the support 2 and bag 6. The resin-based material is a filled epoxy or polyester system with glass flake, glass flock or glass fibre strand, or other inert material as filler. After the resin has set, chocks 3 supporting the machinery are knocked out. <IMAGE>

Description

SPECIFICATION Improvements in and relating to pre-cast antivibration machinery mountings This invention relates to precast anti-vibration mountings for machinery, to reduce the transmission of vibration from machines such as motors, pumps or winches for example to supporting structure to reduce both noise level and vibration caused damage to the support structure by loosening or shearing of bolts for example.

It is known to cast a raft of epoxy resin between the undersurface of the machine, and the support structure, British Patent 1 368 630 describes one such method, which involves supporting the machine on chocks or the like while resin is poured into a space below the machine base and the support structure, defined around the sides by temporary walls of for example rubber strips or metal strips tack welded in place for removal after the resin has set.

Such a method provides a resin block between the machine base and support such as for example a concrete raft, or support girder, which acts as an effective absorber of vibrations. However, it is difficult when pouring the resin in a ship board location to achieve or maintain horizontal attitude of the machine bed. A ship at anchor or at a quay side tends to move, whilst on a slip way the vessel is usually inclined fore and aft, and in a dry dock a ship is likely to be tilted to one side or the other. In such a situation it is difficult to ensure that the upper surface of the resin is poured and sets level, in fact it may overflow the temporary side walls at one side before the top surface of the resin reaches the desired level at the other side, leading to waste of resin and an uneven pad which renders difficult proper leveling of the machine.

An object of this invention is to provide an anti vibration mounting for machinery on ships which will enable such difficulties to be substantially overcome. According to the invention, an antivibration mounting is made by forming one or more pads by locating a concave forming piece in a permeable part of an extrusion bag containing resin in a further bag part, and between a machine base plate and a support structure, squeezing the resin into the end part and within the former and allowing the resin to set. Trimming surplus bag may be effected as required. A bearing plate and material or shim may be interposed beneath/over the forming piece by the machine base plate or support structure.

The resin may be introduced from a squeeze bag manually, and several support pads may be provided each being formed by resin extruded into the space within a U or horseshoe shaped temporary retaining former which may be of rubber or light metal, or alternatively may be of robust construction so as to bear the weight of the machine during the setting of the resin, at each pad location.

The pads may be cast around mounting bolts securing the machine to the support structure against lateral displacement, so that the resin when set and cured cushions the bolt against vibration. The remainder of the space beneath the machine may be filled with the same or a different grade of resin, or filled with a different antivibration material preferably after the wall members have been removed, such as foamed or synthetic plastics material.

The chock material employed in the example hereinafter disclosed is of an epoxy or polyester resin filled system having admixed glass flake, glass flock, glass strand or inert filler, or a material of suitable compatability to make the finished chock of a high density in order to withstand heavy loadings. The advantages the chock resides in that, being extruded into the space available, inclusion of a top facing of steel, stainless steel, brass or bronze, in plate or shim form if required and base facing pieces of a similar material is facilitated.

As this chock forms to the plate on the top face, it allows expansion of the base of the work piece, whereas in a poured chock system the material picks up contours on the moulded face of the chocks and on measuring can be actually thicker, due to the cord marks, tooling or casting marks.

The poured chock cannot be replaced satisfactorily as it will be thicker than a fit replacement chock, and bind depending on cord marks, or casting marks.

The Moly-Chock consists of a bag made of woven rovin fibre glass or another woven material formed eg stitched to the shape of the chock required, allowing variously shaped chocks to be made e.g. horse shoe chock. Inserted into the former bag, to the size of the chock required is a piece of flexible material, cut approximately 1-2 mm smaller than the gap between the base of the foot of the machine being aligned and the base plate.

The bag is dimensioned slightly more than twice the length of the chock required. Inserted into the bag is a tube of polythene which extends 6 mm to 12 mm in the flexible strip which is inside the bag. The epoxy or polyester resin is mixed with the filling material, catalysed, and subjected to vacuum while mixing to prevent aeration of the chocking material. The material is then dropped down the polythene tube into the bag and inside the flexible forming piece. The end of the bag is squeezed in a reverse direction of the intended chock to exclude as much air as possible. A split wooden roller is gripped across the bag a steel shim or specified material is placed on top of the bag, and below if required and the whole slid into the place where the chock is required.

After checking the former is in place of intended use, the excess bag is rolled onto the roller comparable to squeezing a tube of toothpaste. This is rolled until it comes up to the machine face where it squeezes the material, filling the bag completely until the chock becomes a tight fit, and holding the chocking material under constant pressure until curing of the chocking material takes place. Holes placed in the wooden rolling bar can be used with wedges 10 to keep the pressure on the bag, however this could be tied or secured by stapling if wedging with pegs 11 is impracticable. If this method is not possible the bag can be squeezed by two flat boards, hinged with a screw fastening.

After curing, the excess of the chock part can be trimmed off using a suitable tool. The chock of this nature has the advantage that it does not require a dam to retain it; it may be made in horse-shoe shape oran irregularfigure by moulding the flexible slip and cutting and shaping the bag to the required shape. It may also be used in positions outside the horizontal. For example formation of the chock may be effected on board a ship under weigh or riding to anchor.In general substantial reinforcement and viscous materials may be employed in formation of chocks, accompanied by reduction in shrinking that would otherwise be the case; chocking is not dependent on flow of the material as in the case of poured chocking systems: Inserting the material a) after application of vacuum and or b) under load, reduces any tendency to develop air entrapment reducing surface load bearing area.

The chock is of benefit in marine use yet has comparable advantages for anti vibration mountings for turbines, generators and machinery generally.

A preferred method according to the invention will now be described by way of example, with reference to the accompanying drawings which is a diagrammatic illustration of the formation of an anti-vibration mounting pad.

As illustrated in the drawing, a machine base plate 1 is supported above a support such as a concrete raft 2 by chocks 3 only one of which is shown by way of example, to provide a space 4 between the base plate 1 and raft 2. Within the space 4, a plurality of mounting pads can be provided by means of a U-shaped metal wall 5 which is inserted into one end of a bag 6 containing an epoxy resin so as to be wholly within a porous neck 7 of a bag 6 (indicated by crossed hatching, this part of the bag may be of woven textile material while the remainder of the bag 6 is preferably non-porous, having for example a film of polyvinyl chloride or polyethylene bag 12 for example over the same woven substrate. The resin is squeezed from the main part of bag 6 for example by rolling the bag up from the end of roller 13 into the neck part within the U-shaped forming piece 3.Air from the space within the space within the U-shaped wall is expelled through the pores of the porous part 7 of the bag as the resin enters the space. When the resin has been squeezed out of the bag 6, the rolled up bag may be left in place, or alternatively trimmed off after the the resin has set. After the resin has cured, up to two days later, the chocks 3 can be knocked out and the machine base supported directly by the pads of resin. The remainder of the space 4 may if desired be filled with further vibration dampening material such as foam rubber to inhibit among other phenomena noise resonance.

A plate 8 which has been machined to a smooth finish is placed over the wall 5 before the resin is squeezed into the space, on the outside of the bag 6, 7 to provide a smooth riding surface for the machine base 1 on the resin pad as the machine base will ordinarily be rough finished.

Without the intermediary of the plate, there is a risk that the resin would key to the rough machine base 1 preventing relative lateral movement which could lead after use to shearing within the resin pad.

A mounting bolt 9 is shown passing through the space within the U-shaped wall 5 which will be filled with resin so that the bolt 9 will be embedded in the resin pad. The bolt 9 is seated in the concrete raft 2 and engages in an aperture in the machine base, through which a threaded end of the bolt 9 penetrates. A nut and lock nut are placed on this threaded end when the machine bed has settled on the pad after knocking out the chocks 3 to hold the machine against lateral displacement to the raft 2.

The resin pad not only provides a vibration dampening pad between the machine base 1 and the raft or other support structure, but in the embodiment illustrated serves to damp any vibrations arising in the bolt with consequent reduced risk of failure of the bolt due for example to vibration induced shearing.

The method of the invention is particularly adapted to marine use, since because no attempt is made to pour or extrude resin into an open topped pond, the volume into which the resin is introduced being bounded at the time of introduction by the back part 7 and the U-shaped wall 5. As a result there is no risk of spillage of the resin at one side of the space before the space is completely filled, as might happen where an open topped space is inclined or in motion.

Consequently, the method can be used to provide anti vibration mountings for marine machinery such as ships motors, winches, cranes and the like whilst the ship is at anchor or at a quayside in which motion of the ship is inevitable, in a dry dock wherein the ship is likely to be leaning to one side, or on a slip way prior to launch in which case it is likely.to slope from bow to stern.

Claims (12)

1. A method forming an antivibration mounting comprising locating a shaped forming piece in a permeable part of an extrusion bag containing resin in a further impermeable bag part and locating them between a machine base plate and a support surface, squeezing the resin into the permeable part of the bag and within the former and allowing the resin to set thereby forming a resilient pad between the machine base plate and the support surface.

2. A method according to claim 1 wherein the permeable bag part comprises a closed extremity of the bag.

3. A method according to claim 1 or 2 wherein a plurality of resilient pads are formed as set forth in claim 1.

4. A method according to any preceding claim wherein the pad is formed to surround a securing bolt so that the resin when set and cured cushions the bolt against vibration.

5. A method according to any preceding claim wherein the resin material is an epoxy or polyester resin filled system having an inert filler comprising any one or more of glass flake, glass flock or glass fibre strands.

6. A method according to any preceding claim wherein a shim or plate is placed at least over the forming piece, between the latter and the machine base.

7. A method according to claim 6 wherein a further shim or plate is placed below the forming piece, between the latter and the support surface.

8. A method according to any preceding claim wherein the extrusion bag is of woven material stitched to the form of pad required.

9. A method according to any preceding claim wherein the resin and filler are mixed together, catalysed and subjected to vacuum, while mixing, to avoid aeration of the material, then dropped down a polythene tube into the bag and within the forming piece, the bag is then squeezed away from the former to exclude air, and a split wooden roller used to roll the bag up squeezing the resin material into the required space within the forming piece, and the resin allowed to cure.

10. A method of forming an antivibration mounting substantially as hereinbefore described and with reference to and as illustrated in the accompanying drawings.

11. An antivibration mounting having one or more pads or chocks made by a method according to any of claims 1 to 10.

12. Apparatus for use in a method according to claim 1 comprising a forming piece, a bag into which the piece can be inserted having a porous end and a nonporous end, and a resin material and a split wooden roller.