Vibration absorption system
United States Patent 11 1 Toth et a1.  
 1 Apr. 22, 1975 VIBRATION ABSORPTION SYSTEM 176] Inventors: William S. Toth, 302, 17th St.. Wilmette. 111. 60091; James H. Anderson. 1603 Thornwood. Wheaten, Ill. 60187 [22] Filed: May 6, [974 [21] App]. No.: 467,214  
 Primary Examiner-Price C. Faw. Jr. Attorney; Agent, or Firm-Dominik, Knechtel, Godula &amp; Demeur [57} ABSTRACT A vibration absorption system especially useful for supporting roof-top mounted heating and air conditioning units including a base rail, a roofing curb mounted on the base rail and extending upwardly therefrom, the upper edge of the roofing curb provided with roofing securement means for securing sheet roofing materials thereto and in overlaying relation. at least one spacer and support means mounted on the base rail adjacent the roofing curb and linearly spaced along the base rail. At least a pair of levelling and tensioning means, one of each of the levelling and tensioning means mounted on the corresponding spacer and support means, each of the levelling tensioning means provided with independent adjustment means to separately and independently adjust the levelling and tensioning function thereof, the levelling and tensioning means supporting a continuous support beam thereatop to support a heating and air conditioning unit thereon, a continuous top cover shield overlying the continuous support beam and a removably engageable continuous counterflash panel, the top cover shield and the counterflash panel provided with respective mating engagement means to accommodate the removable engagement of the counterflash panel with respect to the top cover shield.  
 23 Claims, 6 Drawing Figures PATENTEDAPRZZIHTS 3.878.655  
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  I I I I I I I I .I I I I I v VIBRATION ABSORPTION SYSTEM BACKGROUND OF THE INVENTION With the advent of more modern architectural struc tures, it has become quite commonplace to construct buildings having essentially flat roofs. or roofs that are slightly pitched as opposed to the gable style roofs. One of the advantages gained by such construction is the ability to position heating and air conditioning units for the building on the rooftop. thereby alleviating the necessity to consume space internally of the building for such large structures. This is especially true in connec tion with air conditioning plants which are generally quite large and in many cases, are add-ons to an existing structure. In one type of installation. the contractor erects a series of steel vertical beams which are laced together by a horizontal steel platform upon which the air conditioning unit is positioned. All of the necessary duct work and piping work is then connected. thereby resulting in an air conditioning installation. The difficulty inherent in such installations is that. generally. modifications must be made to the roofing in order to accommodate the installation of the vertical steel beams. thereby necessitating the roofing-in of the openings created for the installation of ducts. conduit piping and beams. and the protection of these components from the elements. It has been found. however. that such modifications to the roofing often result in water or other leaks immediately beneath the air conditioning unit ultimately causing damage to the interior portion of the building. This is especially true in view of the fact that air conditioning units tend to act as large scale vibratory mechanisms and the constant vibration of such units ultimately causes cracks to reappear in the roofing. and more importantly. creates a noise level which is unsatisfactory to occupants of the building.  
  More recent developments in this art field have dealt with means for isolating the vibration of air conditioning units with a view toward minimizing the problems associated with having to roof-in add-on installation. One of the most recent developments in this connection is displayed in US. Pat. No. 3.72l.l06 which is directed to a mounting for rooftop air conditioners including a curbing which is fixedly mounted on the roof. surrounding an opening in the roof. and across which is positioned a horizontal platform carried on coil springs. The principal concept of such a device is to permit the mounting of the air conditioning unit on a horizontal platform which is. in turn. supported by a series of coil springs of the compression type. thereby to absorb the vibrations caused by the running of the air conditioning unit and minimize the problems associated with the roofing in of such add-on installations. While such devices have had some modicom of success. nevertheless. a variety of problems associated with such an installation continue to exist. For example. the structure depicted in U.S. Pat. No. 3,72l.l06 as well as other such structures have not permitted the preassembling of the curbing structure prior to installation. such that the vibration absorption curbing may be pre-assem bled elsewhere and simply placed in location on the site. As will be evidenced from a review of the aforementioned patent. generally the curbing which provides the ultimate support for the entire structure is not integral with the vibration absorption assembly. but rather. forms an integral part of the roof. As such. the  
 curbing must be roofed in prior to the installation ofthe necessary horizontal platforms. and once the air conditioning unit is installed thereon. repairs to the roofing cannot be easily effected.  
  Other problems which continue to exist relate to the lack of any levelling and tensioning device within the spring isolation unit. whereby variations for the difference in the load characteristics of the air conditioning units cannot be effected. This is extremely important since not all air conditioning units are constructed identically such that different units will have different load characteristics. Unless these load characteristics are compensated for. there is an imbalance of the unit when positioned on the platform. thereby causing additional points of stress to the roof. Additionally. those units which are presently in existence make no provision for the use of inertia type bases which further aid in the absorption of vibration, and hence. a maximum level of vibration absorption has not been achieved. Other problems which have surfaced relate to the failure to provide any sound and/or thermal material on the inside portions of the unit thereby to faciliate the use of the internal portion of the unit as a return air plenum. Furthermore. presently existing curbs cannot be roofed in with the air conditioning unit in place since the platform upon which the units rests interferes with the areas generally to be covered by the roofing material. This therefore necessitates that the system be completely built-up in the field and cannot be prefabricated and pre-assembled and merely placed in location on the site. As concerns the device shown in US. Pat.  
 No. 3.72l.106 specifically. the Hex sheeting provided.  
 about the periphery of the unit to isolate the springs from the outer environment cannot be removed practically to accommodate reroofing where roofing problems ultimately surface and hence. should repairs be necessitated. the owner ofthe building is put to a great expense and inconvience.  
  A variety of other problems continue to exist and it is the purpose of the present invention to alleviate the above-mentioned problems as well as all others.  
 SUMMARY OF THE INVENTION The present invention is intended to provide a vibration absorption curbing assembly which may be preassembled and prefabricated and placed in location on a particular roof site while at the same time permitting an efficient means for roofing in the curbing either prior to or after the positioning of the air conditioning unit onto the supporting structure. In addition. the particular details of construction of the present vibration absorption system permits ease of re-roofing or roofing repairs even while the air conditioning remains in place on the unit. Furthermore. the vibration system provided by this invention provides levelling and tensioning means associated with the vibration absorption means thereby to permit individual varying of the vi bration absorption means and levelling means to accommodate differences in the load characteristics of the particular air conditioning unit positioned thereon. Furthermore. the vibration absorption system provided by this invention is designed to accommodate the addon features of an inertia type block which further facilitates the absorption of vibrations caused by such air conditioning units. thereby to maximize the vibration absorption characteristics of the system.  
  Hence. the present invention provides a continuous base plate having a roofing curb mounted thereon and extending upwardly therefrom. the base plate provided for seatment on a support surface. such as a rooftop. the upper edge of the roofing curb provided with roofing securement means for securing the roofing material thereto in overlaying relation. at least a pair of spacer and support members mounted on the base plate. adjacent the roofing curb and linearly spaced along the base plate. at least a pair of levelling and tensioning means. one of each of the levelling and tensioning means mounted on a corresponding spacer and support means. thereby to be in spaced and supported relation with respect to the base plate each of the levelling and tensioning means provided with independent tension adjustment means to separately and independently adjust the levelling and tensioning function thereof. the levelling and tensioning means carrying a continuous support beam thereon and thereacross to support a heating and air conditioning unit thereatop. a continuous top cover shield overlying the continuous support beam. and a removably continuous counterflash panel. each of the counterflash panel and cover shield. pro vided with respective mating engagement means to accommodate the removal engagement of the counterflash panel with respect to the top cover shield. whereby a rooftop heating and/or air conditioning unit mounted on the continuous support beam is held in supported posture thereatop. while at the same time accommodating independent adjustment of the levelling and tensioning means to adjust for the particular load characteristics of the air conditioning unit and provid ing a maximum amount of vibration absorption of the air conditioning unit and the entire assembly as set forth above being pre-assembled and pre-fabricated and permitting installation of the entire unit on location and on the roof site.  
 OBJECTS AND ADVANTAGES lt is therefore the principal object of this invention to provide a pre-assembled and pre-fabricated vibration absorption mounting curb for rooftop carried air conditioning and heating units which maximizes vibration absorption while at the same time permits individual and separate adjustment of levelling and tensioning means to accommodate the particular load characteristics of a variety of air conditioning units.  
  Another object of the invention is to provide a preassembled vibration absorption mounting curb for rooftop carried air conditioning and heating units. which provides return air attenuation passageways therethrough such that mechanical noise associated with return air ducts is minimized. In addition. the mounting curb of the present invention distributes the load of the unit carried thereon directly onto the structural members of the building roof.  
  A further object ofthe invention is to provide a vibration absorption curbing for rooftop air conditioning units which permits the roofing curb to be roofed-in with roofing material on location. regardless of whether the air conditioning unit is in position. or not yet in po sition. and hence. permits roofing repairs and reroofing to be accomplished with the air conditioning unit remaining in place.  
  Another feature ofthe present invention is to provide a vibration absorption curbing system for mounting rooftop air conditioning units wherein the air conditioning unit is supported and carried on a plurality of l beams positioned adjacent to the curbing and hence. the curbing being only used as a mounting point for the overlaying of roofing material and the l beams actually carry the weight of the air conditioning unit. which fea tures in turn. permit the pre-assembling and prefabrication of the unit off location and concentrating the weight directly to the load bearing members of the building structure.  
  Still another feature of the present invention is the provision of one or more inertia blocks which may be mounted within the unit which function for the purpose of absorbing additional unit vibrations. thereby to maximize the vibration absorption efficiency of the unit.  
  In connection with the foregoing object, it is still a further object to provide a unit which accommodates the add-on of one or more inertia blocks wherein the inertial block consists of a slab of poured concrete which is positioned within the unit and raised upon parallel support slats. the added mass of the concrete add ing to maximize the efficiency of vibration of absorption of the system as a whole. avoiding the necessity of pouring concrete on location.  
  Still a further feature of the present invention is to provide a vibration absorption curbing system wherein the unit includes at least a pair of opposed l beam supports. each of the l beams supporting a compression coil spring. provided with independent compression adjustment means consisting of a compression plate and threaded bolts and further provided with a threaded nut. whereby the threaded positioning of the nut along the length of the bolt will adjust the compression against the spring. thereby to separately adjust the tension associated with each of the springs and accommodate the particular load characteristics of an air conditioning unit positioned upon and supported above the levelling and tensioning springs.  
  In connection with all of the foregoing objects. it is a further object of the invention to provide a vibration absorption curbing system wherein the system is further provided with thermal and sound insulation material completely surrounding the internal portion of the system. such that the system permits the use of one return air duct or opening through the roof. not directly under the return air opening in the unit requiring the air being drawn back into the unit to pass through a portion of the curb thereby attenuating some of the equipment mechanical noise, while still insulating said opening from the outer environment.  
  Still in connection with all of the foregoing objects. it is a further object wherein the system is provided with a removable counterflash panel which extends between the top cover shield and the roofing curb in overlapping relationship thereby to conceal and insulate the levelling and tensioning springs from the outer environment while still permitting the ease of removal thereof. thereby to accommodate re-roofing or roofing repairs without the need for removing the air conditioning unit from thereatop.  
  Further features of the invention pertain to the particular arrangement of the elements and parts whereby the outlined and additional operating features thereof are attained.  
  The invention both as to its organization and method of operation. together with further objects and advantages thereof will best be understood by referring to the following specification taken in connection with the accompanying drawings. in which:  
  FIG. I is a plan view of the vibration absorption system of the present invention;  
  FIG. 2 is a side elevational view. partly broken away. showing the relationship between the roofing curb. levelling and tensioning means. support beam and top cover rail;  
  FIG. 3 is a perspective view. partly broken away. showing the manner in which the counterflash panel is removably engageable with respect to the top cover shield.  
  FIG. 4 is a side elevational view. in cross section. showing the relationship between the respective elements. taken in the direction of the arrows along the line 4-4 of FIG. I.  
  FIG. 5 is a side elevational view. partly in cross section. showing the details ofthe levelling and tensioning spring taken in the direction of the arrows along the line 55 of FIG. 4: and  
  FIG. 6 is a top view showing the top support plate of the levelling and tensioning assembly. taken in the direction of the arrows along the line 66 of FIG. 5.  
  With reference to FIGS. 1 through 3 ofthe drawings. the overall design ofthe system proposed herein is illustrated. The vibration absorption curb. generally re ferred to by the numeral 10 is shown to include a base plate l2. which is of generally rectangular configuration and extends around the complete rectangular configuration and extends around the complete periphery ofthe curb It). Securely affixed along the outer peripheral edge of the base plate 12 is a roofing curb 14 which is shown to include an attachment foot l6 which functions to securely affix the roofing curb 14 to the base plate l2. The attachment foot extends rearwardly for a short distance and then includes an upstanding vertical section 17 which in turn. progresses into a canted section 18. the terminal end of the canted section 18 extending vertically upwardly in a second upstanding vertical section 19 having the upper end turned inwardly and then downwardly in the form of a U-shaped upper section 20. having the opposed end. in turn. extending inwardly into an attachment flange 2]. The upper wall of the U-shapcd upper section 20 is prt vided with a roof mounting rail 22. which in the present embodiment is shown to be formed of wood. thereby to facilitate the nailing engagement of roofing materials thereto. All of which will be more fully explained hereinat&#39;ter.  
  The roofing curb 14 extends completely around the peripheral edge ofthe base plate 12 in the manner illustrated in FIGS. I through 3 of the drawings.  
  As will be appreciated from FIG. 1 of the drawings. a series of linearly spaced I beams 24. are each mounted on the base plate [2 interiorly of the roofing curb 14. each of the I beams 24, of course. formed by the base 25. gusset 26 and atop rail 27. The top rail in turn. supports a housing 29. which accommodates the levelling and tensioning assembly 30 therein. The levelling and tensioning assembly 30 is more clearly illus trated in FIG. 5 of the drawings. and is shown to include a base plate 32. which rests on the top rail 27 of the l beam 26. Along one of the side edges of the base plate is a vertical upstanding support 33 which may be formed as an adjustable support by means of a lower base section 34. and a threaded bolt 35, which is thrcadedly secured therein by means of a pair of nuts (ill 36. Alternatively. the vertical support 33 may simply be a vertical upstanding from the base plate 32 in the man ner shown in FIGS. 2 and 3 ofthe drawings. The assem bly 30 further includes a top plate 38. which in turn. carries a threaded bolt 30 extending downwardly from the lower surface thereof. lnterposed between the top plate 38 and the base palte 32 is a compression spring 42 which seats at its lower end against the base plate 32. and at its upper end seats against a compression plate 44 (FIG. 5]. The compression plate 44 is held in fixed position atop the spring 42 by means of a threaded nut 45. which is threadedly mounted on the threaded bolt 40 and clearly adjusts the compression against the spring 42 by vertical positioning along the threaded bolt 40.  
  It will further be observed from a view of FIG. 1 of the drawings that the plurality ofI beams 24 having the levelling and tensioning assembly 30 there-atop carry a support beam 46 thereatop. the support beam 46 being continuous around the upper periphery of the vibration absorption curb 10. Hence. the support beam 46 similarly assumes a rectangular configuration as shown in FIG. 1 of the drawings. As more clearly shown in FIG. 4 of the drawings. the support beam 46 assumes a shaped configuration and is formed by a support foot 47.11 structural center section 48 and an upper section bar 49. It will be appreciated that since the support beam 46 is carried peripherally by the plurality of levelling and tensioning assemblies 30 which are. in turn. supported on the plurality of l beams 24. the support beams 46 are therefore not carried by the base rail. nor are the same affixed to the roof when the vibration absorption curb II) is installed in location on a roof. Hence. it will be appreciated that each of the le elling and tensioning assemblies 30 may be adjusted and further. it is clear that the weight. or load of the air conditioning unit 200 is carried by the (shaped support beam 46. rather than by the roofing curb 14. such that the weight may be effectively distributed by and between the levelling and tensioning assemblies 30 and minimize the direct weight load against the roof.  
  The upper portion of the curb I0 is completed by a top cover shield 50 formed by an outer side wall 51. a top wall 52.1111 interior wall 53 and a step wall 54. The undersurface of the step wall 54 carries an inverted U- shapcd channel 55 for a purpose to be described more fully hereinafter. The lower leading edge of the outer side wall 5] is provided with an upturned flange 57 which again. functions for a purpose to be more fully described hereinafter. Constructionally. the top cover shield 50 is fixedly secured to the upper support bar 49 of the support beam 46 as more clearly shown in FIG. 4.  
  It will further be observed that the base plate I2 is provided with an upturned U-shaped channel 58 which is in vertical alignment with the downturned U-shaped channel 55 fixedly secured to the top cover shield 50. Between the respective L&#39;shaped channels 55 and 58. is carried sheet insulation material 60 around the complete interior periphery of the structure as is represented in FIG. I of the drawings. It will therefore be apparent that the insulation material 60 is carried around the complete interior portion of the vibration absorption curb I0 and functions to act as both a thermal and sound barrier with respect to the interior portion ofthe assembly. Hence. in the event that any openings are placed in the roof internally of the curb 10. the insulation sheet material 60 functions as both a thermal as well as a sound barrier.  
  The assembly is completed by a removably engageable counterflash panel 65 which is formed by relatively straight vertical lower section 66. a canted section 67 and an upper engagement section 68 having a downturned flange 69. carried along the outer peripheral edge thereof. It will be apparent from a view of FIGS. 3 and 4 of the drawings. that the counterflash panel 65 is removahly engageable with the top cover shield 50 by the engagement and disengagement of the respective upturned flange 57 of the top cover shield 50 and the downturned flange 69 of the counterflash panel 65.  
  It now becomes apparent that insofar as the vibration absorption curb assembly ll) is concerned. the complete structure may be prefabricated and preassembled prior to installation at a particular job site. Once the curbing is transported to a job site the base plate 12 thereof is fivedly secured to the rooftop after which sheet roofing material may be applied over the roofing roof mounting rail 22. Since the mounting rail 22 is formed of wood. the sheet roofing material may be easily nailed thereto. Obviously. the roofing operation is conducted with the countcrflash panel 65 remo ed therefrom to expose the roof mounting rail 22. In this manner. it will be appreciated that the curb ll) may easily be roofed into an existing roof in an extremely watertight and weatherproof sealing arrangement. while still permitting the complete cxposture of the levelling and tensioning assemblies when the counterflash panel 65 is removed from around the periphery of the curb 10. Once the curb 10 has been roofed in as indicated above. the counterllash panel 65 is merely engaged onto the top cover shield 50 by inter connecting the respective flanges 57 and 69 of the top cover shield 50 and counterflash panel 65 respectively. as clearly shown in FIG. 4 of the drawings. The air conditioning unit 200 is shown to include legs which overlay the upper support bar 49 of the support beam 46 and resting over the top wall 52 of the top cover shield 50. It will also be observed as indicated previously. that the load of the air conditioning unit 200 is carried by the support beam 46 which is in turn resting upon the top plate 38 of the levelling and tensioning assembly 30. In this manner. while the load ultimately rests on the roof via the l beam 24. the fact of the matter is the load is not carried by the roofing curb l4, and hence. no load function is being carried by the roof per se where the roofing has been interrupted to provide for the curb [0. Furthermore. by the provision of the eye beams 24 as well as the base plate 12 whatever load is exerted by the air conditioning 200 against the roof generally. is distributed such that there is less stress against any given point along the roof. thereby minimizing the danger ofcraeks in the roofing material and hence. water or other leaks to the interior of the building.  
  it will be further observed from FIGS. 1 and 4 of the drawings. that the curb l0 of the present invention may further be provided with a plurality of T-shaped structural spacers 70 formed by a base support slat 72 and having a dividing rail 74 upstanding therefrom and ccntrally disposed with respect thereto. The structural spacers are positioned between opposed beams 46 and rest against the interior portion of the support foot 47 of each of the opposed beams 46. as shown in phantom Ill in FIG. 4 of the drawings. Each pair of structural steel spacers is therefore capable of carrying an inertia block (H0. 4) and it will be apparent that more than one of said inertia block 75 may be carried by a single vibration absorption curb 10. The ideal embodiment contemplated by the present invention is that each of the inertia block 75 is formed by a poured concrete slab. generally including lifting lugs (not shown) set into the concrete such that the slab may be lifted by a crane or other suitable lifting device into position. The function of the concrete inertia block 75 is to further facilitate the absorption of vibration in view ofthe fact that an increase in the amount of mass will absorb more vibrations. Hence. by the provision of the levelling and tensioning assemblies 30. including the compression spring 32, as well as the provision of an inertia block 75. the curb 10 of the present invention maximizes the efficiency of the unit by absorbing the maximum possible vibrations generated by the air condi tioning unit carried thercatop.  
  It will therefore be appreciated by reference to the above description that the curbing assembly ll] of the present invention. clearly provides a system which may be pre-fabricated and pre-asscmbled away from the situs of installation and transported in substantially complete form to the job site As indicated abo\ e. the curb 10 may be lowered on the roof on the desired place and permits the roofing operation to commence immediately. whereby roofing material is laid over the roofing curb 14. including the canted section 18 thereof and the roofing materials securely affixed to the roof mounting rail 22. It is further significant that the wood mounting rail 22 is stepped in order to accept the roofing insulation and canted in order to facilitate the flashing by a roofing contractor. The structural steel spacers 70 may be positioned during manufacture between opposed support beams 46 and welded in position thereby to accommodate one or more inertia blocks 75 therebetween. Hence. concrete inertia block 75 may be lifted by any suitable lifting mechanism and placed into position prior to the positioning of the air conditioning unit thereatop.  
  At this point. the air conditioning unit is then positioned on the support beam 46 and the levelling and tensioning operation may be accomplished by adjusting the threaded nuts 45 carried on the threaded bolts 40 incident to the levelling and tensioning assembly 30. In this manner. particular load characteristics of various air conditioning units may be compensated for after the unit has been placed in position on the curb 10 in order to make the unit perfectly level. The installation is completed by engageably mounting the counterflash panels 65 by interconnecting the upturned flange 57 of the cover shield 50 with the downturned flange 69 of the eounterflash panel 65. in the manner described above. Upon completion of the assembly. the entire assembly is rendered weatherproof and \veathertight. and by virtue of the provision of the sheet insulation material 60 the interior portion of the assembly is rendered soundproof.  
  As a further feature of the invention. due to the constructural features thereof. the unit may be provided with an interior built-in drain pan to capture rainwater passed through the air conditioning unit. As shown in FIG. I ofthe drawings. the drain pain may be accommodated adjacent one side edge of the unit as represented by the letter D in FIG. I. In this manner. the problems associated with having water drain directly on the roof surface and hence. having a puddle or pool thereon. potential damage is further eliminated.  
  lnsofar as the counterflash panel 65 is concerned. it will be appreciated that by providing a removably counterflash panel 65, in the event roofing repairs are necessary. or roofing is desirable. the counterflash panel 65 may easily be removed by disengaging the respective flanges 57 and 69. thereby exposing the roof mounting rail 22 of the roofing curb 14. It will therefore be appreciated that an entire roof may be completely re-roofed or repairs effected without the necessity of removing the air conditioning unit 200 from the curb 10. In point of fact. a new roof may easily be laid and the roofing carried over the roofing curb l4. and securely mounted to the roof mounting rail 22. after which the counterflash panel 65 may be engageably mounted with the top cover shield 50 to once again close off the unit and render the same weathertight. It will further be appreciated that the counterflash panel 65 is so designed and constructed as to not only engage with the top cover shield 50. but also extend downwardly in overlapping relationship with respect to the roofing curb 14. Hence. it is virtually impossible for the interior portion ofthe curb to be exposed to the elements.  
  The provision of the insulation material 60 internally of the curb l0 permits the use ofonc or more openings through the rooftop for both air intake. air exhaust. power wiring. gas. stream or water piping. In this manner. and by the provision of the insulation 60. the interior portion of the building is insulated both thermally and audibly with respect to the air conditioning unit 200 carried thereon. as well as with respect to the outer environment, which is a feature heretofore not provided in any of the units developed to date. As shown in FIG. 1 of the drawings. the insulation 60 may be carried around the complete side periphery internally of the curb l0. thereby to completely insulate the interior portion thereof.  
  lnsofar as levelling and tensioning assemblies are concerned. it will be appreciated that these assemblies not only function to level the air conditioning unit 200, carried thereatop. but also. at least partially function to at least further absorb the vibrational forces exerted by the air conditioning unit 200. In other words. the compression spring 42 provided as part of the levelling assembly 30 will function to absorb some of the vibrational forces generated and these along with the inertia blocks 75 will produce a unit which provides a minimum of 90% isolation efficiency with respect to the vibrational forces exerted.  
  An additional advantage obtained by virtue of the curbing provided with the present is the fact that in many roofing operations. it is difficult to position cranes or other such load carrying structures adjacent the buildings being constructed. and hence the ability to position rooftop air conditioning and heating plants in position is difficult. This is especially so where in order to position such units in place on the rooftop it is necessary to use rolling gantries on the rooftop prior to laying the roofing material thereon. As has been pointed out previously. many of the present existing systems require that the roofing curbs be fixedly secured to the rooftop prior to mounting the units thereon. and where these units are utilized it is virtually impossible to use a rolling gantry on the rooftop. The  
 curbing of the present invention. however. permits the entire unit. with the heating and air conditioning unit mounted thereon to be positioned on the rooftop and a series of such units may be positioned on the same rooftop. one at a time. prior to laying the roof thereon. and hence. a rooling gantry may be used on the rooftop. Once all of the units and curbs thereunder have been positioned. the last stage of completion involving the laying of the roof may then be completed. It is apparent that it is not desirable to place any heavy loads on the roof. once the roofing paper and gravel have been placed on the roof may easily be damaged. causing subsequent water leaks. Hence. by permitting the installation of the subject curbing with the heating and air conditioning units positioned thereon. prior to laying the roof. and providing the ability to roof in the unit after such installations. many installations requiring rolling gantries on the roof during installation are rendered much more efficient.  
  ln addition. the curbing of the present invention functions. as previously indicated. to properly level the heating and air conditioning units mounted thereon. As a result. all of the drain systems associated with the air conditioning unit will operate properly. In many of the presently existing systems once the air conditioning unit becomes cocked or improperly positioned. the draining systems associated with the unit will not function properly. hence. the curbing of the present invention renders the unit much more efficient and permits the proper functioning of the drain system.  
  It will therefore be appreciated by virtue of this invention as described and claimed herein that a highly efficient and yet pre-assembled and prefabricated vibration absorption curb system has been developed which is efficient either for original construction or add-on construction relative to an existing building permitting the easy installations of air conditioning units on the rooftops thereof. Furthermore. it will be appreciated that the curb of the present invention permits the unit to be completely roofed-in even while the air conditioning unit is positioned thereon. while at the same time rendering the complete assembly weathertight and waterproof. It will also be appreciated that since the load of the air conditioning unit is not brought to bear directly against the rooftop. or the curb mounted on the rooftop. but rather is carried by a con tinuous support beam which is. in turn. carried by the levelling and tensioning assemblies, the load is distributed and no stress is placed at any particular point of the roof. but rather. the load is concentrated directly onto the structural members of the building, thereby minimizing the possibility of roof damage over time. Furthermore the provision of individual levelling and tensioning assemblies permits the separate adjustment of such assemblies to accommodate the peculiar or partieular load characteristics of different types of air conditioning units. thereby enlarging upon the variety of uses to which the curbing can be adjusted. depending upon the types of air conditioning units to be installed. The results are apparent that the current curb permits the optional use of inertia blocks formed of concrete which further facilitate in the absorption of undesirable vibrational forces generated by the air conditioning unit once in use. such that a minimum of vibration isolation may be achieved. It is therefore to be appreci ated that all the above objects and advantages have been accomplished by means ofthe curb structure depicted herein and the various embodiments thereof. to provide an extremely economic vibration absorption curb system which may be pre-assemblied and prefabricated and transport. fully assembled to the location where desired.  
  While there has been described what at present is considered to be the preferred embodiments of the invention. it will be understood that various modifications may be made therein. and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.  
 What is claimed is:  
  l. A pre-assembled vibration absorption system for rooftop mounted heating and air conditioning units. comprising in combination.  
 a continuous base plate for seatment upon an underlying surface such as a rooftop.  
 a continuous roofing curb mounted on said base plate and extending upwardly therefrom.  
 the upper edge of said roofing curb provided with roofing securement means for securing the roofing material thereto in overlaying relation.  
 at least a pair of spacer and support means mounted on said base late adjacent said roofing curb and linearly spaced along said base plate. at least a pair of levelling and tensioning means. one of each of said levelling and tensioning means mounted on a corresponding spacer and support means thereby to be in spaced and supported relation with respect to said base plate and roof pitch.  
 each of said levelling and tensioning means provided with independent tension adjustment means to separately and independently adjust the levelling and tensioning function thereof.  
 said levelling and tensioning means carrying a contin uous support beam thereon and thereacross to support a heating and air conditioning unit thereatop.  
 a continuous top cover shield overlying said continuous support beam.  
 and a rcmovably engageable continuous conterflash panel. each of said cover shield and counterflash panel provided with. respectively. mating engagement means to accommodate the removable engagement of said counterflash with said top cover shield.  
 whereby said vibration absorption system may be preassembled and placed into position on location. thereby permitting the independent varying of said levelling and tensioning means dependent upon the particular load characteristics of a heating and air conditioning unit supported thereon. by the independent and separate adjustment of said adjustment means associated with said levelling and tensioning means. while at the same time permitting the unit to be roofed in with any appropriate roofing material.  
  2. The vibration absorption system as set forth in claim 1. wherein said roofing securement means comprises a top rail mounted linearly along the upper edge of said roofing curb. said top rail accommodating the overlay fastening of roofing material thereto.  
  3. The vibration absorption system as set forth in claim 2 above. wherein said top rail is formed of wood. thereby to accommodate the nailing engagement of roofing materials to said top rail.  
  4. The vibration absorption system as set forth in claim 1 above. wherein said spacer and support means comprises a plurality of eye beams mounted on said base plate and upstanding therefrom. the upper surface of each of said eye beams supporting one of said levelling and tensioning means.  
  5. The vibration absorption system as set forth in claim I above. wherein each of said levelling and said tension means includes a base plate. a vertical support mounted on said base plate and extending upwardly therefrom adjacent the side edge thereof. a top plate carried by said vertical support in parallel orientation with respect to said base plate and space therefrom. a pressure plate carried on and spaced from said top plate along the under surface thereof. pressure plate adjustment means interposed between the under surface of said top plate and said pressure plate thereby to permit the vertical adjustment of said pressure plate relative to said top plate. and spring means interposed between said pressure plate and said base plate. said spring means tending normally to bias said pressure plate away from said base plate. and said top plate supporting and carrying said continuous support beam thereon whereby a load positioned atop said support beam is biasingly held by said levelling and tensioning means.  
  6. The vibration absorption system as set forth in claim 5 above. wherein said pressure plate adjustment means comprises a threaded bolt mounted along the undersurface of said top plate and extending downwardly therefrom to an aperture provided in said pres sure plate. and a nut screw-threadedly mounted on said bolt immediately above said pressure plate whereby the vertical orientation of said pressure plate relative to the vertical height of said bolt may be adjusted by screwing and unscrewing said nut.  
  7. The vibration absorption system as set forth in claim 1 above. wherein said counterflash panel disen gageably engages said top cover shield and extends downwardly beyond the upper edge of said roofing curb. thereby to insulate the upper edge of said roofing curb from the outer environment.  
  8. The vibration absorption system as set forth in claim 7 above. wherein said top cover shield includes a rearwardly and reversely turned flange extending along the bottom edge thereof. and said counterflash panel includes a forwardly and reversely turned flange along the upper edge thereof. such that said respective rearwardly and forwardly turned flanges may be matingly engaged to form a removable engagement means for removably engaging said counterflash panel with respect to said cover shield.  
  9. The vibration absorption system as set forth in claim 1 above. wherein said continuous support beam is C-shaped in configuration and is continuous about the upper peripheral eges of said system and supported solely by said levelling and tensioning means.  
  [0. The vibration absorption system as set forth in claim I. wherein said roofing curb is canted from top to bottom thereby functioning to direct water flow away from the said system.  
  ll. The vibration absorption system as set forth in claim 1 above. wherein said base plate is provided with an upturned U-shaped channel mounted along the length thereof and said top cover shield is provided with a down-turned U-shaped channel mounted along the length thereof. and insulation sheeting material is mounted within and between said respective U-shaped channels on said base plate and said top cover shield.  
 thereby to further insulate the interior portion of said system from both noise and the elements.  
  12. The vibration absorption system as set forth in claim 11 above. wherein said respective U-shaped channel on said base plate and said top cover shield respectively are fixedly secured to said respective base plate and top cover shield. thereby to provide a fixed mounting for said insulation sheeting material.  
  13. The vibration absorption system as set forth in claim 1 above. wherein said system further includes a plurality of laterally extending structural spacers carried between opposed portions of said continuous sup port beam. and a weighted inertia block carried between adjacent and parallel oriented structural spacers. said weighted inertia block functioning to facilitate the absorption of vibration emanating from the heating and air conditioning unit carried by said system.  
  14. The vibration absorption system as set forth in claim [3 above. wherein said structural spacers are T shaped in configuration and each of said slab of concrete carried by said supported between adjacent parallel oriented T-shaped structural spacers.  
  15. A pre-assembled vibration absorption system for rooftop mounted heating and air conditioning units comprising in combination.  
 a continuous base plate for seatment upon an under lying surface such as a rooftop.  
 a continous roofing curb mounted on said base plate extending upwardly therefrom.  
 the upper ege of said roofing curb provided with roofing securement means for securing the roofing material thereto in overlaying relation.  
 a plurality ofl beams mounted on said base rail and upstanding therefrom. said I beams being mounted and positioned in horizontally opposed relation on opposing sides of said base plate.  
 at least a pair of levelling and tensioning means. one of each of said levelling and tensioning means mounted on a corresponding l beam. thereby to be in spaced and supported relation with respect to said base plate.  
 each of said levelling and tensioning means provided with independent tension adjustment means to separately and independently adjust the levelling and tensioning function thereof.  
 said levelling and tensioning means carrying a continuous support beam thereon and thereacross to support a heating and air conditioning unit thereatop.  
 a continuous to cover shield overlying said continuous support beam.  
 and a removably engageable continuous counterflash panel each of said top cover shield and counterflash panel provided with. respectively. a mating engagement means to accommodate the removabie engagement of said couterflash panel with respect to said top cover shield.  
 whereby said vibration absorption system may be pre-assembled and placed into position on loca tion. thereby to permit the independent varying of said levelling and tensioning means to adapt to the particular load characteristics of a heating and air conditioning unit supported thereon. by the sepa rate adjustment of said adjustment means associated with each of said levelling and tensioning means. while at the same time permitting said system to be partially and permanently roofed in with appropriate roofing material.  
  16. The vibration absorption system as set forth in claim 15. wherein said roofing securement means comprises a wooden top rail extending along said roofing curb thereby to accommodate the overlay fastening of roofing material thereto.  
  17. The vibration absorption system as set forth in claim 15 above. wherein each of said levelling and tensioning means includes a base plate. a vertical support mounted on said base plate. and extending upwardly therefrom. a top plate carried by said vertical support in parallel orientation with respect to said base plate. and spaced therefrom.  
 a pressure plate carried on and spaced from said top plate along the undersurface thereof.  
 pressure plate adjustment means interposed between the undersurface of said top plate and said pressure plate. thereby to permit the vertical adjustment of said pressure plate relative to said top plate. and spring means interposed between said pressure plate and said base plate. said spring means tending normally to bias said pressure plate away from said base plate. whereby a load positioned on said continuous support beam carried on said levelling and tensioning means may be levelled by the independent and separate varying of each of said pressure plate adjustment means while at the same time partially absorbing vibrations incident to the operation of a heating and air conditioning unit positioned thereatop by virtue of said spring means.  
  18. The vibration absorption system as set forth in claim 17 above. wherein said pressure plate adjustment means comprises a threaded bolt mounted on the undersurface of said top plate and extending downwardly therefrom through an aperture provided in said pressure plate, and said threaded bolt being provided with a threaded nut in mating engagement thereon and positioned immediately above said pressure plate thereby to vertically adjust the difference between said pressure plate and said top plate by the screwing and unscrewing of said nut relative to said bolt.  
  19. The vibration absorption system as set forth in claim 18, wherein said continuous support beam is U- shaped in configuration and continuous about the upper peripheral edge of said system. said U-shaped support beam being supported solely by said levelling and tensioning means whereby a heating and air conditioning unit is positioned on said continuous support beam may be levelled by the independent and separate adjustment of said tension adjustment means.  
  20. The vibration absorption system as set forth in claim 15 above. wherein said counterflash panel is disengagably engageable with said top cover shield and extends downwardly therefrom beyond the upper edge of said roofing curb. thereby to insulate the upper edge of said roofing curb from the outer environment.  
  21. The vibration absorption system as set forth in claim 20 above. wherein said top cover shield includes a rearwardly and reversely turned flange along the bottom edge thereof and said counterflash panel includes a forwarding and reversely turned flange along the upper edge thereof. such that said respective rearwardly and forwardly turned flanges may be matingly engaged to form a removable engagement means for removably engaging said counterflash panel with respect to said top cover shield.  
  22. The vibration absorption system as set forth in claim 15 above. wherein said base plate is provided Ill aligned in opposed relation. one of each of said pair of l beams mounted adjacent the opposed short sides of said system. each one of said pair of said I beams carrying a levelling and tensioning means thereon. and said continuous support beams being carried in turn by said levelling and tensioning means whereby heating and air conditioning units may be supported thereon in level disposition regardless of the particular load characteristics thereofv