GB2265669A

GB2265669A - Reciprocating compressor dynamic balancer

Info

Publication number: GB2265669A
Application number: GB9306836A
Authority: GB
Inventors: Robert Adolph Ackermann; Constantinos Minas; Evangelos Trifon Laskaris
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1992-04-03
Filing date: 1993-04-01
Publication date: 1993-10-06
Anticipated expiration: 2013-04-01
Also published as: GB2265669B; JPH0626455A; GB9306836D0

Abstract

A support stand (6, Fig. 1) fixed at one end to the compressor (4) and supported on a base (12) through isolation mounts (10) has dynamic balancers 50 fixed to opposite legs of the stand. Each balancer comprises a multi-leaf spring 54 fixed at opposite ends to a support 52 and carrying weights 68 at its centre. The balancer is tuned to resonate at the compressor operating frequency by adding or subtracting weights 68. <IMAGE>

Description

LTNEAR COMPRESSOR DYNAMIC BALANCER CROSS-REFERENCE TO A RELATED APPLTCATTON This application is related to co-filed patent application corresponding to U.S. Patent Application Serial No. 635or 07/862,688 (RD-21988) Laskaris, entitled "A Flexible Suspension for an Oil-Free Linear Motor Compressor".

Background oftheTnvention Field of the Invention This invention relates to vibration balancers of the type that are used with linear compressors. Such structures of this type, generally, eliminate the axial vibration created by a linear compressor by tuning the balancer to the operating frequency of the linear compressor.

DescrIption of the Related Art The reciprocating mass in a linear compressor produces an axial vibration that is transmitted to the compressor base. If this vibration is not eliminated, the transmitted force will produce severe shaking of the compressor base and auxiliary equipment. The noise and fatique produced in the auxiliary equipment will lead to objectionable noise levels and to early failure of the compressor system Therefore, a more advantageous compressor system would be presented if such amounts of vibration could be eliminated.

The principles of dynamic vibration reduction were embodied in a dynamic vibration absorber invented by Frahm in 1909. The principle of the absorber is that a small mass attached to the main mass through a spring will balance the transmitted force from the main mass when the natural frequency of the attached spring mass system is made to resonate at the frequency of the disturbing force. For this design, Frahm showed that the main mass does not vibrate and no vibratory forces are transmitted though the mounts supporting the main mass. Therefore, a still further advantageous vibration reduction system would be presented if the principles as set forth by Frahm could be applied in reducing the vibration associated with a linear compressor.

It is apparent from the above that there exists a need in the art for a dynamic balancer which is capable of dampening out vibration, and which at least equals the vibration dampening characteristics of the known vibration dampeners, but which at the same time substantially dampens out all the vibration created by a linear compressor. It is a purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure Summary of the Invention Generally speaking, this invention fulfills these needs by providing a dynamic balancer for a compressor which comprises a compressor means rigidly attached to one end of a compressor stand, at least two vibration balancer means rigidly attached to said stand such that said balancer means are located at a predetermined distance away from each other and dynamically opposed to any vibration created by said compressor means, and an isolation mounting means attached to another end of said compressor stand.

In certain preferred embodiments, the compressor is a linear compressor. Also, the vibration balancer means consists of a base which securely holds leaf springs and a vibrating mass located at the center of the leaf springs. Finally, the isolation mounts consist of soft, rubber mounts.

In another further preferred embodiment, the balancers are resonantiy tuned to the operating frequency of the compressor which effectively eliminates all the axial vibration created by the compressor.

The preferred dynamic balancer, according to this invention, offers the following advantages: lightweight; easy assembly; excellent vibration dampening characteristics; good stability; excellent durability; good economy; and high strength for safety. In fact, in many of the preferred embodiments, these factors of vibration dampening characteristics, durability and economy are optimized to an extent considerably higher than heretofore achieved in prior, known dynamic balancers.

Brief Descrintion of the Drawings The above and other features of the present invention which will become more apparent as the description proceeds are best understood by considering the following detailed description in conjunction with the accompanying drawings wherein like characters represent like parts throughout the several views and in which: Figure 1 is a schematic illustration of a linear compressor with vibration balancers and isolation mounts, according to the present invention; Figure 2 is a side plan view of the vibration balancer, according to the present invention; and Figure 3 is a top view of the vibration balancer, according to the present invention.

Detailed Description of the Invention With reference first to Figure 1, there is illustrated dynamic balancer 2.

Balancer 2 includes compressor 4, compressor stand 6, support 8, isolation mount 10, base 12 and vibration balancer 50. Compressor 4, typically, is a 10 hp compressor which is capable of producing a peak axial reciprocating force (F) of 700 lb as compressor 4 vibrates. Compressor 4 is rigidly attached to stand 6 by conventional fasteners. Stand 6, preferably, is constructed of steel.

Vibration balancers 50, which are shown in an end view, are rigidly attached to stand 6 by angle supports 8. Supports 8, preferably, are constructed of steel.

Supports 8 are attached to stand 6 and balancer 50 by conventional weldments.

Located between compressor stand 6 and base 12 are isolation mounts 10.

Mounts 10, preferably, are constructed of any suitable soft, elastomeric materiaL With respect to Figure 22 the details of vibration balancer 50 will now be discussed. Balancer 50 is fabricated by mounting leaf springs 54 on to a base 52 that securely holds leaf springs 54 in place and mounts rigidly to compressor stand 6 (Figure 1). Leaf springs 54, preferably, are constructed of high strength, carbon steel. The leaf springs 54 are separated by spacers 58, 60 located at both ends and the center of the springs 54, respectively, and securely clamped at the ends by the clamping brackets 62, conventional fasteners 64 and conventional washers 66.Spacers 58, 60, preferably, are constructed of any suitable metallic material and are 0.03 inches thick to ensure that the leaf springs 54 do not contact each other. Balancing weights 68 are mounted in the center of leaf springs 54 and held in place with locating pin 70 (Figure 3), conventional fasteners 72 and conventional washers 74. Critical aspects of balancer 50 fabrication are: 1. The mounting of springs 54 on the base 52.

2. The positioning of the dynamic weights 68 in the center of the springs 54.

3. The flexibility of adjusting the dynamic weight 68, and 4. The clamping of the weights 68.

With respect to Figure 3, springs 54 were mounted on base 52 with a 0.002 inch interference between spring tabs 74 and base 52 by heating springs 54 to approximately 125'F to expand springs 54 over the ends of base 52.

Tabs 74, preferably, are machined by conventional machining techniques to be approximately 1.000 inches wide. From 1 to 15 springs 54 are mounted on base 52 and separated with spacers 58, 60. The complete spring assembly is rigidly mounted to base 52 with end clamps and bolts 62 and 64, respectively.

The interference fit and the end clamps 62 provide a very secure mounting for the leaf springs 54 and prevents any longitudinal or transverse movement of the springs relative to the base 52 or to one another.

The positioning of the dynamic weights 68 in the center of the springs 54 is accomplished by cutout 76 in the center of base 52 which positions a conventional fixture 78 that holds and locates the lower weight 68 during the clamping of the dynamic weight assembly 56. Fixture 78, preferably, is constructed of any suitable metallic material. Clamping of the weights 68 in the center of the springs 54 also provides flexibility during assembly and tuning of the balancer 50 to the operating frequency by enabling weights 68 to be easily added or removed from the assembly 56. The final clamping of the assembly with the bolts 72 securely holds the weights 68 in place during operation.

As discussed earlier, linear compressor 4, typically, is a 10 hp machine capable of producing a peak 700 lb axial reciprocating force (F). Dynamic balancers 50 were designed to cancel this force and eliminate axial vibration transmitted to base 12. The optimum balancer design for this application is one that achieves a large axial spring stiffness to produce a peak balancer inertia force equal to the machine's axial reciprocating force (F) with small deflections.

A balancer with low spring stiffness leads to large deflections, high stresses in the springs, and a bulky design. Balancer 50 achieves a high spring stiffness by employing multiple, rigidly supported, leaf springs 54 supporting a centrally located vibrating mass 56. The high stiffness at the leaf springs 54 is achieved by rigidly supporting the ends 74 of the springs 54 so that the overall stiffness is composed of a bending and longitudinal tensile stiffness. This produces a nonlinear stiffness function that increases with the axial deflection of the leaf sprigs 54, and leads to a stiff, low deflection, vibratory system. Balancer 50 is also easy to tune to the compressor's operating frequency by adjusting either the number of leaf springs or the central balancer mass.

The assembled balancer is made operational by tuning the spring mass system to resonant at the compressor operating frequency. This operation is performed by adjusting the dynamic weight 56, i.e., either adding or subtracting weight 68 from balancer 50, while measuring its natural frequency with a conventional accelerometer according to conventional frequency measuring techniques.. The accelerometer is mounted on the dynamic mass and the system is excited with a conventional impulse force hammer. The flexibility of being able to easily change the dynamic weight of the balancer makes this a simple pre-operational adjustment.

Claims

CLAIMS:

1. A dynamic balancer for a compressor which is comprised of: a compressor means rigidly attached to one end of a compressor stand; at least two vibration balancer means rigidly attached to said stand such that said balancer means are located at a predetermined distance away from each other and dynamically opposed to any vibration created by said compressor means; and an isolation mounting means attached to another end of said compressor stand

2. The balancer, according to claim 1, wherein said compressor is further comprised of: a linear compressor.

3. The balancer, according to claim 1, wherein said vibration balancer means is further comprised of: a leaf means; a leaf spring means rigidly attached to said base means; a spacer means located between said leaf spring means; and a dynamic weight means substantially rigidly attached to said leaf spring means.

4. The balancer, according to claim 3, wherein said base means is further comprised of: a cutout.

5. The balancer, according to claim 3, wherein said leaf spring means is further comprised of: spring tabs.

6. The balancer, according to claim 3, wherein said dynamic weight mass is further comprised of: a fastener, at least one weight; and afixture.

7. A method of dampening out a vibration created by a compressor including a compressor, a compressor stand, vibration balancers having leaf springs and a dynamic weight assembly, and an isolation mount means, wherein said method is comprised of the steps of: attaching said isolation mount means to one end of said compressor stand; attaching said vibration balancers to said compressor stand; attaching said vibration balancers to said compressor stand such that said balancer means are located at a predetermined distance away from each other; operating said compressor such that said compressor creates a vibration force at a constant frequency; and tuning said vibration balancers to resonate at said constant frequency by adjusting, if needed, said dynamic weight assembly of said vibration balancers to create a dampening resonant force such that said vibration force of said compressor is dampened out by said dampening resonant force of said dynamic weight assembly.

8. The method, according to claim 7, wherein said step of tuning said vibration balancers is further comprised of the step of: altering an amount of weight in said dynamic weight assembly.

9. A balancer substantially as hereinbefore described with reference to the accompanying drawings

10. A method substantially as hereinbefore described with reference to the accompanying drawings.