GB1602866A

GB1602866A - Mounting of vibratory machines

Info

Publication number: GB1602866A
Application number: GB18605/78A
Authority: GB
Original assignee: FMC Corp
Current assignee: FMC Corp
Priority date: 1977-05-13
Filing date: 1978-05-10
Publication date: 1981-11-18
Also published as: IT7823281A0; JPS53140475A; DE2820915A1; FR2390638B1; CA1104108A; AU520309B2; JPS5675338U; FR2390638A1; ZA781772B; NL7804336A; BR7802693A; MX148987A; AU3452878A

Description

(54) IMPROVEMENTS IN OR RELATIN G TO THE MOUNTING OF VIBRATORY MACHINES (71) We, FMC CORPORATION, a Corporation organised and existing under the laws of the State of Delaware, United States of America, of 200 E. Randolph Drive, Chicago, State of Illinois, United States of America, 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: The present invention relates to the mounting of vibratory machines.

In one previously proposed type of vibratory machine, a working member is movably mounted on a base. A drive member is connected between the base and the working member to impart vibratory motion to the working member. The working member may, for example, be an -elongated trough which receives material to be conveyed longitudinally along the trough as the trough is vibrated, or the working member may be a screen which receives a load to be sifted through the vibrating screen. Other types of vibrating machines also employ a base member, a working member, and a drive member connected between the base member and the working member to impart a vibratory motion to the working member.

Despite efforts to limit the vibratory motion to the working member, vibration in the base is inevitable. If the machine is installed on the ground, no serious problems wi]l be created by the vibration of the base.

qIf, however, the machine is installed in a building, or on some other supporting structure or member, the vibration of the machine can weaken or damage the building or other structure, particularly if the vibrations are of a frequency at or near the natural frequency of the supporting structure.

Because of the destructive effect a vibrating base of a vibratory machine can have on the supporting structure on which the machine is mounted, it is well known to provide isolation springs between the base and the supporting structure to insulate the latter from the vibrations of the former. It has been proposed to use, as isolation springs, elastomer pads or blocks having contact surfaces which are horizontal for engagement with the base member. In other words, a central axis perpendicular to the interface with the base is vertical in each of these isolation pads.

Blocks made of elastomer (which term as used herein shall be understood to include rubber and any elastic substance resembling rubber) are quite yieldable in shear but much less yieldable under compression.

Thus, an elastomer block (that is, with parallel upper and lower surfaces) constitutes a stiff spring when resisting forces directed perpendicularly to said upper and lower surfaces, but constitutes a soft spring when resisting lateral forces (that is, any force parallel to the upper and lower surfaces of the block).

The principal vibratory force which must be isolated from the supporting structure in the usual vibratory machine (such as a material conveyor) is the longitudinal vibration created by the reaction to the driving oscillations which propel the material forward in steps. The soft resistance of the blocks when oriented with horizontal contact faces to this longitudinal vibration effectively isolates the vibration from the supporting structure.

However, the elastomer blocks with horizontal contact faces, because of the characteristics of the elastomeric material, also present little resistance to lateral forces which permits an undesired lateral sway of the conveyor. Moreover, the stiffness of the elastomer blocks to vertical forces when the contact faces are horizontal, although effective to support the conveyor, result in poor isolation of vertical vibrations and permits these destructive vibrations to be transmitted to the supporting structure.

According to the present invention there is provided an assembly comprising a vibratory machine having a base, a work member, means for supporting the work member for movement relative to the base, and a drive member for effecting vibration of said work member relative to the base, and a mounting system mounting the machine on a stationary supporting member, said mounting system comprising elastomer isolation blocks mounted between said base and said supporting member on each side of the longitudinal center-line of the base, said base having, on each side of said center-line, surfaces which face downwardly and outwardly, and said blocks having surfaces which face upwardly and inwardly in parallel relation to said inclined surfaces on the base to receive said base surfaces in supporting relationship.

Further according to the present invention, there is provided an assembly comprising a vibratory machine having a base, a work member, means for supporting the work member for movement relative to the base in a vertical plane extending longitudinally, of the member, and a drive member to effect vibration of said work member in said plane relative to the base with the vibration having a component extending longitudinally of the work member, and a mounting system mounting the machine on a stationary supporting member said mounting system including elastomer isolation blocks having opposing parallel faces engaging, respectively, parallel and spaced apart support faces on the base and said stationary support member, said blocks offering stiff resistance in compression to forces transmitted from said base to said stationary supporting member normal to said engaging faces and offering soft resistance in shear to forces transmitted from said base to said stationary member parallel to said engaging faces, with said blocks being mounted between said base and said supporting member on each side of the longitudinal centerline of the base, wherein the support faces on the machine base are on each side of said centerline and face downwardly and outwardly and wherein said support surfaces on said stationary support member face upwardly and inwardly, said surfaces on the base and on the stationary supporting member lying in planes parallel to the longitudinal centerline of the base, each of said elastomer isolation blocks being oriented by said support surfaces to resist vertical force in both compression and shear thereby to support said machine while minimizing compression forces transmitted to said stationary supporting member, and to resist transverse components of vibration in both compression and shear, while limiting to shear the resistance to longitudinal com ponents of vibration of said work member.

The invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a side elevation of a vibratory machine with portions being broken away, and a mounting system therefor; Figure 2 is an end elevation taken on line 22 of Figure 1; and Figures 3A, 3B and 3C show schematically three different arrangements of isolation blocks for a vibratory machine.

There is shown in Figure 1 a vibratory machine 10 having a base 12 and a work member 14. Although the machine may be any vibratory machine in which a work member is oscillated longitudinally with respect to a base, we have shown for illustrative purposes a material conveyor. The work member 14 of the material conveyor 10 is in the form of a trough which receives material 15 at the left end (as viewed in Figure 1) and transports the material to the right end.

The work member 14 is mounted for movement relative to the base by means of leaf springs 16. Each leaf spring is secured at one end, by bolts 18, to the work member and is secured, at the opposite end, by bolts 20, to the base. The leaf springs, which are inclined slightly from the vertical, define the path of movement of the work member as perpendicular to the inclined leaf springs.

Thus, at each end, the work member moves in the direction of the arrows 22.

A drive unit 24 is connected between the base 12 and the work member 14. The drive unit includes a motor 26 mounted on the base and a crankshaft 28 rotatably mounted in bearing blocks 30 which are also mounted on the base. The crankshaft 28 is driven by the motor through pulley 32, secured to the crankshaft, and belt 34. Rotation of the crankshaft imparts to work member 14 a vi- bratory motion in a vertical plane extending longitudinally of the work member, through a crank 36 which is rotatably received on the crankshaft and pivotally connected to the work member 14.

Since the vibratory motion of work member 14 is in the direction of arrows 22, the work member vibration will have a horizontal, or longitudinal component 22h and a vertical component 22v. The horizontal and vertical components of the vibratory motion of the work member create reactionary horizontal and vertical components of vibration in the base.

The elements of Figure 1 described above are well-known conventional vibratory machine elements used heretofore.

The base 12 is elongated and, as shown best in Figure 2, of rectangular cross-section with a longitudinal centerline 40 extending therethrough. The base 12 is supported on a member 46, which is usually stationary and is frequently a structural unit such as the floor of a building, or a built up platform or stand to support the conveyor. The vibratory reaction to the oscillations of the conveyor create longitudinal and vertical vibrations in the base. These base vibrations, particularly if close to the natural frequency of the support member, can be destructive if not isolated from the support structure.

It is well known to provide elastomer blocks between the base and the supporting member, but these blocks are conventionally oriented in an upright, or vertical, position (that is, with the upper and lower surfaces thereof lying in parallel horizontal planes).

As will now be explained with reference to Figures 3A, 3B and 3C, the orientation of the elastomer block will affect the spring characteristics thereof.

As shown in Figure 3A, when the contact face F of an elastomer block B, which is supported on member S, is horizontal, the weight of a vertically acting load L (such as gravity) acts to compress the block. In this orientation, the block B acts as a stiff spring to this vertical force.

As shown in Figure 3B, when the contact face F of an elastomer block, which is supported on member S, is vertical, the weight of a vertically acting load L (such as gravity) acts in shear. In this orientation, the block B acts as a soft spring to the vertical load.

It should be noted that when the block B is too soft to vertical forces, the block must be increased in area to support the weight of the machine. The increase in size of the block increases the longitudinal stiffness of the block, thereby transmitting a greater longitudinal force to the support surface S.

The transmission of a greater force to support surface S defeats the objective of reducing forces transmitted to the support member.

As shown in Figure 3C, when the contact face F of an elastomer block, which is supported on member S, is inclined at an angle between the vertical and horizontal (say, at an angle of 45" to each), the weight of a vertically acting load (such as gravity) acts partly in compression and partly in shear.

In this orientation, the characteristics of the spring to vertical forces fall between the stiffness of the orientation of Figure 3A and the softness of the orientation of Figure 3B.

The orientation of the block shown in Figure 3C does not increase the stiffness of the block to longitudinal forces.

As shown in Figures 1 and 2, L-shaped brackets 42L and 42R are secured at two or more points along each side, respectively, of the base. The lower surfaces 44L and 44R of the brackets define contact surfaces which are inclined to face downwardly and outwardly (away from the centerline 40 of the base). Preferably, the contact surfaces define an angle of approximately 45" from the horizontal, although angles of from 30 to about 70" can be used under some circumstances depending on the specific vertical and horizontal spring characteristics required.

Two or more brackets 48R, 48L (one for each base bracket 42R, 42L) are mounted on the stationary support on each side, respectively, of the centerline 40 of the base in registration with the brackets on the base as shown in Figures 1 and 2. Each bracket 48R, 48L has an upper surface 50R, 50L inclined to face upwardly and inwardly (toward the centerline 40 of the base), parallel, respectively, to the surfaces 44R, 44L of the base brackets 42R, 42L.

An elastomeric block 52 is received between each of the pairs of complementary surfaces 44R-50R, 44 > 50L to support the vibratory machine 10 on the stationary support member 46. It is believed that a comparison of the schematic diagrams of Figures 3A, 3B and 3C will clearly demonstrate the desirable effects of our elastomer isolation block orientation, which is similar to the arrangement illustrated in Figure 3C.

By placing the block 52 at an intermediate angle (Figure 2), we have created a spring less stiff than conventionally mounted springs but yet less soft than a block totally in shear.

By adjusting the angle of inclination (relative to the horizontal) from between 30 and 70 , we can make the spring stiffer (than a block at 450) to either vertical or horizontal forces or softer.

Thus, it will be understood that the stiffness of the elastomeric springs acting in the vertical direction can be softened by placing the blocks at an angle (say, 45 ), with the upper faces of the blocks facing upwardly and inwardly. It should also be noted that in the arrangement of Figure 3A, where the upper surfaces of the blocks are horizontal, the springs defined thereby are soft in the lateral direction. This softness in the lateral direction subjects the vibratory machine to lateral sway. However, our orientation of the blocks at an angle (as shown in Figures 2 and 3C) not only acts to soften the springs in the vertical direction but acts to stiffen the springs in the lateral direction.

The difficulty with the arrangement of the springs of Figure 3A is that the springs are so stiff in the vertical direction that destructive vibratory forces are transmitted through the springs to the stationary support. The arrangement of Figure 3B would substantially eliminate the transmission through the springs of the destructive vertical vibratory force but would produce springs too soft to adequately support the conveyor. Our arrangement of Figure 3C and Figure 2 soften the springs but leaves them stiff eneough to adequately support the conveyor.

An examination of Figure 1 will show that the longitudinal vibrations of the work members act on the elastomer blocks in shear so that the springs remain soft to these forces and do not transmit them to the support structure.

It should be noted, as shown in Figure 2, that central axes 54L and 54R through the blocks and perpendicular to the faces thereof intersect at a point identified as a roll center RC. These points (which define a roll center axis extending through two or more RC points) constitute roll centers because they are the points about which the elastomer blocks 52 offer the least resistance to roll. In order to prevent an undesirable roll, we arrange the angle of inclination of the blocks to assure that the axes 54L and 54R intersect above the center of gravity CG of the vibratory machine (when under normal load) so that the vibratory machine will not have a tendency to lean.

Thus, in the embodiment particularly described, the contact faces of the blocks (which preferably are located on either side of the conveyor) are tilted inwardly toward the conveyor. In this orientation, the vertical load of the conveyor acts on the elastomer block partly in compression (which offers greater resistance to deflection) and partly in shear (which offers less resistance to deflection). Consequently, the inclined elastomer block defines a spring of intermediate stiffness to the vertical load (and vibration) of the conveyor instead of the maximum stiffness provided by a elastomer block with horizontal load bearing surfaces. The softer spring for vertical vibrations results in significantly less destructive forces transmitted to the supporting structure.

At the same time, the resistance to lateral sway of the conveyor is significantly increased by the fact that a lateral load on the elastomer block, when the contact face of the block is inclined toward the conveyor acts partly in compression and partly in shear, instead of all in shear as when the load receiving face of the block is horizontal.

It should be noted that the inclination of the elastomer blocks does not alter the desirable soft spring reistance to longitudinal vibration achieved when the elastomer block has the load receiving face in a horizontal plane. The elastomer block, when inclined however resists longitudinal vibration only in shear.

WHAT WE CLAIM IS:- 1. An assembly comprising a vibratory machine having a base, a work member, means for supporting the work member for movement relative to the base, and a drive member for effecting vibration of said work member relative to the base, and a mounting system mounting the machine on a stationary supporting member, said mounting system comprising elastomer isolation blocks mounted between said base and said supporting member on each side of the longitudinal centreline of the base, said base having, on each side of said center-line, surfaces which face downwardly and outwardly, and said blocks having surfaces which face upwardly and inwardly in parallel relation to said inclined surfaces on the base to receive said base surfaces in supporting relationship.

2. An assembly comprising a vibratory machine having a base, a work member, means for supporting the work member for movement relative to the base in a vertical plane extending longitudinally of the member, and a drive member to effect vibration of said work member in said plane relative to the base with the vibration having a component extending longitudinally of the work member, and a mounting system mounting the machine on a stationary supporting member said mounting system including elastomer isolation blocks having opposing parallel faces engaging respectively, parallel and spaced apart support faces on the base and said stationary support member, said blocks offering stiff resistance in compression to forces transmitted from said base to said stationary suppcsrting member normal to said engaging faces and offering soft resistance in shear to forces transmitted from said base to said stationary member parallel to said engaging faces, with said blocks being mounted between said base and said supporting member on each side of the longitudinal centerline of the base, wherein the support faces on the machine base are on each side of said centerline and face downwardly and outwardly and wherein said support surfaces on said stationary support member face upwardly and inwardly, said surfaces on the base and on the stationary supporting member lying in planes parallel to the longitudinal centerline of the base, each of said elastomer isolation blocks being oriented by said support surfaces to resist vertical force in both compression and shear whereby to support said machine while minimizing compression forces transmitted to said stationary supporting member, and to resist transverse components of vibration in both compression and shear, while limiting to shear the resistance to longitudinal components of vibration of said work member.

3. An assembly according to claim 2, wherein the elastomer isolation blocks are oriented with the engaging faces thereof at such an angle to the horizontal that the central axes through the blocks which are perpendicular to the engaging faces thereof, intersect at a plurality of points along a longitudinal roll center axis above the center of gravity of the vibratory machine when the machine is under normal load.

4. An assembly according to any one of claims 1 to 3, in which the upwardly and inwardly facing surfaces of the blocks are at

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. It should be noted, as shown in Figure 2, that central axes 54L and 54R through the blocks and perpendicular to the faces thereof intersect at a point identified as a roll center RC. These points (which define a roll center axis extending through two or more RC points) constitute roll centers because they are the points about which the elastomer blocks 52 offer the least resistance to roll. In order to prevent an undesirable roll, we arrange the angle of inclination of the blocks to assure that the axes 54L and 54R intersect above the center of gravity CG of the vibratory machine (when under normal load) so that the vibratory machine will not have a tendency to lean. Thus, in the embodiment particularly described, the contact faces of the blocks (which preferably are located on either side of the conveyor) are tilted inwardly toward the conveyor. In this orientation, the vertical load of the conveyor acts on the elastomer block partly in compression (which offers greater resistance to deflection) and partly in shear (which offers less resistance to deflection). Consequently, the inclined elastomer block defines a spring of intermediate stiffness to the vertical load (and vibration) of the conveyor instead of the maximum stiffness provided by a elastomer block with horizontal load bearing surfaces. The softer spring for vertical vibrations results in significantly less destructive forces transmitted to the supporting structure. At the same time, the resistance to lateral sway of the conveyor is significantly increased by the fact that a lateral load on the elastomer block, when the contact face of the block is inclined toward the conveyor acts partly in compression and partly in shear, instead of all in shear as when the load receiving face of the block is horizontal. It should be noted that the inclination of the elastomer blocks does not alter the desirable soft spring reistance to longitudinal vibration achieved when the elastomer block has the load receiving face in a horizontal plane. The elastomer block, when inclined however resists longitudinal vibration only in shear. WHAT WE CLAIM IS:-

1. An assembly comprising a vibratory machine having a base, a work member, means for supporting the work member for movement relative to the base, and a drive member for effecting vibration of said work member relative to the base, and a mounting system mounting the machine on a stationary supporting member, said mounting system comprising elastomer isolation blocks mounted between said base and said supporting member on each side of the longitudinal centreline of the base, said base having, on each side of said center-line, surfaces which face downwardly and outwardly, and said blocks having surfaces which face upwardly and inwardly in parallel relation to said inclined surfaces on the base to receive said base surfaces in supporting relationship.

an angle of between 30 and 70" to the horizontal.

5. An assembly substantially as hereinbefore described with reference to Figures 1, 2 and 3C of the accompanying drawings.