US 2439219 A
Description (OCR text may contain errors)
A RCH ROO SUBSTITUTE FOR MISSING XR J. C. O'CONNOR L APPARATUS FOR TRANSMITTING INTENSE VIBRATIONS FOR PERFORMING woax CROSS REFERENCE I April 6, 1948.
Filed June 9, 1944 ATTORNEYS Patented Apr. 6, 1948 APPARATUS FOR TRANSMITTING INTENSE VIBRATION S FOR PERFORMING WORK v John C. OConnor, Dayton, Ohio Application June 9, 1944, Serial No. 539,585
This invention relates to vibratory apparatus and in particular to the means employed to connect the resilient members to the base and to the part to be vibrated.
Many industrial operations are performed by vibrators. For example in the manufacture of concrete blocks wet concrete is placed in a mold and the mold is severely vibrated to compact the material and to secure intimate contact between the ingredients. Many conveyors employ a vibrating trough and many screening operations employ a vibrated screen. In these and similar applications one dificult problem is to provide a satisfactory mounting arrangement between the base structure, the vibrated part and the resilient members connecting these parts. If the resilient members or springs are clamped tightly to the base or the vibrated member, high local stresses are set up at the junction which lead to early failure of the spring. Likewise, if the resilient members are loosely mounted the resulting play or backlash allows destructive wear to occur between the parts. Thus it is diflicult to design a mounting for the resilient member of a vibratory apparatus which will simultaneously permit large amplitude vibration and long life of the resilient member.
It is an object of this invention to provide a mounting arrangement for the resilient member of a vibratory apparatus which minimizes local stresses in the member and thus contributes materially to the life of the resilient member.
Another object is to provide a mounting arrangement for the resilient member of a vibratory apparatus which will accommodate large amplitude of vibration without a material shortening of its useful life.
Another object is to provide a mounting for the resilient member of a vibratory apparatus which will allow a certain amount of freedom of the resilient member without introducing frictional losses which would result in destructive heating.
A still further object is to provide, in an ap paratus employing a straight beam or bar as the resilient member, a mounting for the resilient member which while preventing a transverse deflection oliers little restraint to a longitudinal motion produced by the bending of the beam.
These and other objects and advantages are apparent from the following description in which reference is made to the accompanying drawings.
In the drawings:
Figure I is a side view, partly in section, of a vibratory structure.
Figure II is an end elevation of the structure shown in Figure I.
Figure III is a perspective view of a wooden resilient member with the stress relieving members in place before assembly into the vibratory structure.
Figure IV is a perspective view of a resilient metallic bar with the stress relieving members attached.
These specific drawings are intended to illustrate a preferred form of the invention Without defining the scope of the invention.
According to the invention the local stresses in a resilient member employed as the spring in a vibratory apparatus are relieved by inserting pads of a universally flexible material such as rubber between the resilient member or spring and the mounting clamps. Further, to prevent any scufling between the spring and the flexible material which may occur due to the longitudinal movement of the spring the flexible material is adhesively bonded to both the spring and the adjacent surfaces of the clamping members.
It has been found when the flexible material is not bonded that a scufiing or sliding motion occurs between the spring and the pads and the friction resulting therefrom generates sufficient heat to melt the flexible material and thus to destroy its serviceability. The adhesive bonding prevents this relative motion between the surfaces by distributing the relative movement throughout the flexible material so that no portion is stressed beyond its elastic limit and consequently little heat is generated.
The bonding of the flexible material to the clamping surfaces and to the spring offers the added advantage that small variations in tuning of the spring may be obtained by varying the clamping pressure. If one attempts to get this adjustment when the flexible material is not bonded it merely squeezes out of the space without materially changing the frequency. Also when the material so squeezes out higher stresses are produced at the edges of the clamps and these higher stresses soon lead to'failure of the flexible material. By adhesively bonding the flexible material to both the spring and the clamp this squeezing out is prevented and no local stresses are allowed to develop.
In the specific examples shown in the. drawings a base H3 is provided with pedestals H and I2 at its ends and an electromagnet l3 intermediate its ends. A vibratory member M to which may be attached a platform of a compacting machine, a mold box, a portion of a conveyor, or in fact any structure to be vibrated is carried on 3 a resilient beam or spring I 5 which may be made of wood, metal or a combination of wood and metal.
Each end of the beam I5 is carried on a stress relieving mounting comprising pads [6 of a universally flexible material such as rubber supported by backing strips IT. This assembly is clamped to the top of the pedestal II by a clamping bar l8 held in place by stud bolts l9 anchored in the pedestal II. The flexible pads l6 are adhesively bonded to the adjacent surfaces of the beam l5 and to the backing strips H. The clamping bar I8 is pulled down until the flexible material bulges out slightly from between the beam l5 and the backing strips I! but not enough to squeeze the material out adjacent the surfaces of the beam I5 and the backing strips ll.
The vibratory member l4 and an armature cooperating with the electromagnet l3 are on opposite sides of the beam l5 and are connected by bolts 2| thus clamping the beam l5 between them. To prevent local stresses being generated in the beam l5 at the edges of the vibratory member l4 and the armature 20 flexible pads 22, bonded to the beam [5 and to backing strips 23, are interposed between the beam [5 and the vibratory member M on the one side and the armature 20 on the other side. The sole purpose of bonding the backing strips I1 and 23 to the flexible pads l6 and 22 is to allow the structure to be disassembled without destroying the bond between the pressure transmitting surfaces and the flexible pads. These backing strips may be omitted and the pads l6 and 22 bonded directly to the adjacent clamping surfaces without loss of operating efficiency.
While rubber or similar materials have been used in similar structures as a spring it is used here in the form of a stress reliever and does not materially contribute to the resiliency of the beam 15 in determining the natural frequency of the vibration. Its chief purpose is to allow the relative longitudinal motion between the beam l5 and the pedestals H and i2 which accompanies a transverse deflection of the mid point of the beam. If such motion were not allowed the beam would be stressed in tension as well as bending as it is deflected and the tension forces would be of such magnitude as to cause slipping between the beam and'the clamps. The provision of the flexible pads l6 accommodates this motion without subjecting the beam to the high tensile stresses.
Figure III shows the beam I5 and the resilient pads I6 and 22 with their backing strips I! and 23 attached thereto. It will be noticed that the flexible pads in their unstressed state are rectangular parallelepipeds while after they are assembled in the machine and stressed they tend to become barrel shaped.
Figure IV shows a metallic beam 24 equippe with flexible pads Mia and 22a and backing strip-s Ila and 23a. This beam may be substituted for the wooden beam l5 in those applications where a large amplitude vibration is not used. A choice of one material in preference to another is dictated by the desired amplitude of vibration, the allowable weight of the structure, and the cost. It has been found in general that selected wood, for a given weight, is stronger than steel and allows a higher amplitude of vibration. With either material, in order to relieve stresses in the resilient beam at its clamping points, it is necessary to use a flexible material and in order to secure reasonable life of the flexible material it is 4 necessary to bond the flexible material to the adjacent surfaces. By so bonding the material the allowable limit on the amplitude of vibration is set by the bending stresses in the resilient beam alone. I
Since, in the prior art constructions without the 1. In apparatus for performing work by vibration employing a tuned vibratory system, a resilient subassembly for the vibratory system consisting of a beam adapted to vibrate transversely to its length, and pads of universally flexible material bonded to the beam and interposed between the beam and its support.
2. In apparatus for performing work by vibration, in combination, a mass to be vibrated, a frame, a resilient subassembly for supporting the mass from the frame, means for generating vibratory force, the mass and the resilient subassembly forming a resonant vibratory system having a natural frequency substantially equal to the frequency of the vibratory force, the resilient subassembly consisting of a beam and pads of a universally flexible material adhesively bonded to the beam and interposed between the beam and the frame.
3. In apparatus for performing work by vibration, in combination, a mass to be vibrated, a frame, a resilient subassembly cooperating with the mass to form a tuned Vibratory system for supporting the mass from the frame, means for inducing vibration of the mass on the resilient subassembly, the subassembly consisting of a beam adapted to vibrate transversely to its length and pads of resilient material adhesively bonded to the beam and interposed between the beam and the remainder of the vibratory system.
4. In apparatus for performing work by vibration, in combination, a mass to be vibrated, a"
frame, a resilient subassembly supporting the mass from the frame and forming with the mass a vibratory system, means for exciting resonant vibration of the system, the resilient subassembly being adapted to withstand high amplitudes of vibration and consisting of a beam vibrating transversely to its length and pads of universally flexible material bonded to the beam and interposed between the beam and its supports, the pads serving to distribute the forces applied to the beam to prevent localized high intensity stresses without materially altering the resonant frequency of the vibratory system.
5. In apparatus for performing work by vibration employing a tuned vibratory system, in combination, a beam that is vibrated transversely of its length at amplitudes sufficient to destructively heat rubber clamping pads frictionally engaging the beam, and pads of flexible material adhesively bonded to the beam and interposed between the beam and clamps holding the beam, whereby the frictional energy loss and heating of the pads is reduced without reduction in the amplitude of vibration of the beam.
6. In apparatus for performing work by vibration employing a tuned vibratory system, in combination, a beam that is vibrated transversely of its length at amplitudes sufficient to destructively heat rubber clamping pads frictionaliy engaging the beam, and pads of rubber adhesively bonded to the beam and interposed between the beam and clamps holding the beam,
whereby the frictional energy loss and heating of the pads is reduced without reduction in the amplitude of vibration of the beam.
JOHN C. O'CONNOR.
REFERENCES CITED The following references are of record in the 11m of this patent:
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