Abstract: A compact externally pressurized gas bearing spindle assembly can increase the degree of vacuum in a vacuum chamber. In a spindle assembly wherein a rotary shaft is provided in a housing through a bearing gap, and compressed gas is introduced into the bearing gap to support the rotary shaft in a non-contact manner relative to the housing, an exhaust gas suction device for sucking gas discharged from the bearing gap is provided inside the housing or the rotary shaft. The bearing gap near the outside of the housing is smaller than the other bearing gap. Near the bearing gap near the outside of the housing, a non-contact seal gap is formed to prevent leakage of compressed gas into the vacuum chamber in a non-contact manner.

Abstract: A rotary air bearing (A) as shown in the Figure has a journal (2) provided with a pair of outwardly presented tapered surfaces located opposite the tapered surfaces on the journal, and a low friction liner (6) bonded to the tapered surfaces on the hub and having tapered surfaces which are separated from the tapered surfaces of the journal by small air gaps (g).

Abstract: A hydrodynamic bearing is provided comprising a shaft having a pair of spaced apart conical bearings supporting a surrounding sleeve for rotations. The sleeve comprises a single piece rather than the two-piece design separated by a rubber expansion joint of the prior art. Instead upper and lower slots are cut into the sleeve, and the rings are pressed or otherwise tightly fitted into each slot. The single piece sleeve which also incorporates the bearing seats for the conical bearings on the shaft, is made of aluminum, while each ring is made of steel (as is the shaft and bearing cones). As the temperature rises at which the hydrodynamic bearing is operated, the sleeve expands axially putting the bearing seat closer to the cone, effectively compensating for the thinning of the fluid which supports the bearing seat and sleeve for rotation relative to the cone. Meanwhile, the steel ring, being of the same material as the shaft, prevents the aluminum sleeve from expanding radially away from the cone.

Abstract: A drive axle assembly includes a stationary member and a rotating member spaced apart from said stationary member to form a gap. A fluid bearing is formed between the stationary and rotating members by filling the gap with a fluid. The fluid creates a bearing surface between the stationary and rotating members. The fluid is pressurized to provide radial and thrust load support for the rotating member as it rotates with respect to the stationary member.

Abstract: A double sleeve type dynamic bearing comprises a fixed shaft having at least one end fixedly mountable to an apparatus in which the bearing is utilized, a rotary sleeve arranged coaxially with the fixed shaft so that a first fine gap is formed therebetween, a fixed sleeve arranged coaxially with the rotary sleeve so that a second fine gap is formed therebetween, and a lubrication oil filled in the fine gaps. The first fine gap and the second fine gap each have an open end exposed to air outside the bearing and an opposite end that is not exposed to the air, the opposite ends being in communication with each other. A holding member holds the fixed shaft and the fixed sleeve and is disposed adjacent to a lower end surface of the rotary sleeve to form a third fine gap between the holding member and the lower end surface of the rotary sleeve. The third fine gap is formed with a thrust dynamic pressure producing groove, and opposite ends of the first and second fine gaps meet each other through the third fine gap.

Abstract: It is an object of the invention to provide a thrust dynamic pressure bearing in which an unsymmetrical contact during rotation is prevented from occurring, and a dynamic pressure space is prevented from being clogged with abrasion powder generated by a contact at starting and stopping. In the thrust dynamic pressure bearing of the invention, a flange disposed on a shaft is tapered as moving form toward the outer circumference thereof, so that a dynamic pressure space between a thrust bearing face of a housing and a thrust receiving face of the shaft during rotation becomes wider toward the outer circumference thereof. Even if the shaft is tilted with respect the housing during rotation, therefore, it is possible to prevent an unsymmetrical contact of the thrust receiving face of the shaft in the vicinity of the circumference against the thrust bearing face of the housing, from occurring.

Abstract: A hydrodynamic type bearing unit comprises a shaft member 2, a bearing member 4 and a bearing clearance formed between the shaft member 2 and a bearing member 4 to produce a hydrodynamic pressure during the rotation of a shaft member 2. The bearing clearance is composed of a first clearance C1 on one axial side and a second clearance C2 on the other axial side and the first and second clearances C1 and C2 are mutually oppositely inclined against an axial direction.

Abstract: A discrete fluid dynamic bearing comprising a fluid dynamic bearing including a bearing cone mounted on a sleeve and defining in cooperation with a bearing seat having a surface facing an outer surface of the bearing cone across a fluid bearing gap, a first seal establishing a pressure gradient from a distal end of the sleeve toward the gap of the fluid dynamic bearing and a second seal on an opposite side of the fluid dynamic bearing from the first seal for establishing a positive, higher pressure toward the fluid bearing gap, the press established by the first and second seals maintain the fluid in the gap during relative rotation of the surfaces of the fluid dynamic bearing.

Abstract: A bearing assembly including a bearing cone (50) having a crowned bearing surface (56) with V-shaped grooves (60) that are shallow at their apex (62) and deepest at the outer edges (52, 54). When mated with a female bearing seat, lubricating fluid builds up along the midline of the bearing surface as the bearing seat rotates about the bearing cone.

Abstract: For an impeller pump, the seal/bearing unit has two rotor-stator pairs of tapered sleeves arranged back-to-back. The sleeves have a spiral groove, and convey barrier-liquid from an entry-mouth in an entry-chamber to an exit-mouth in an exit-chamber. Having two sleeves gives the units mechanical stability, thrust support capability, and resistence to vibrations and other abuses. The tapered sleeves may be arranged wide-narrow-wide, or narrow-wide-narrow. The sleeves may be mounted for sliding in the housing and on the shaft, or may be fixed to the housing or shaft.

Abstract: A fluid dynamic bearing usable in a spindle motor where the bearing is defined between two relative rotating surfaces which are open to the air at both ends, allowing the use of a fixed shaft. At one end of the shaft, at least one high volume, low stiffness seal is used, in combination with a low volume, high stiffness seal. The pressure differential between these two seals is balanced by one or more high stiffness, low volume seals spaced axially away along the shaft.

Abstract: An improved capillary seal for use with a hydrodynamic bearing is disclosed, which provides a stronger or stiffer seal for a fluid dynamic bearing motor which is open at both ends, and is used with top cover attached motors utilizing fluid dynamic bearings. The design of the capillary seal uses centrifuigal force to actively push the oil back into the FDB while it is spinning, combined with the capillary tension which holds oil in the FDB during stationary periods. Also, the seal design comprises two walls which converge toward an apex near an adjacent fluid dynamic bearing. This design allows air, trapped within the seal and the associated FDB, to be expelled, eliminating air bubbles from the fluid dynamic bearing.

Abstract: A hydrodynamic bearing useful as a bearing cartridge or as the cartridge may be incorporated into a spindle motor or the like, where the bearing includes a stationary shaft and two independent bearings, comprising a top cone and a bottom cone separated by a segment of the shaft. The bearing includes a sleeve rotating around and surrounding the shaft, and the top cone and bottom cone and defining a narrow gap between the sleeve and the shaft and cones. Sealing plates are supported on the sleeve to seal off the ends of the bearing and are located along the shaft beyond the cones. A gap also exists between an interior surface portion of each cone and the shaft. Thus, separate flow paths are established, one around the top cone and one around the bottom cone. By providing two independent paths, the flow rates do not have to be the same in each conical flow path for the bearing seals to function properly.

Abstract: A spindle motor has a rotor, a stator and an air dynamic pressure bearing for supporting the rotor for rotation about a rotational axis relative to the stator. The air dynamic pressure bearing comprises a first dynamic pressure bearing portion and a second dynamic pressure bearing portion. The first dynamic pressure bearing portion comprises a convex side bearing member having a conical convex portion, a concave side bearing member having a conical concave portion receiving the conical convex portion, and dynamic pressure generating grooves formed on one of a surface of the conical convex portion and a surface of the conical concave portion.

Abstract: A bimetallic part is formed from metals or comprises metals with different thermal expansion coefficients. A first element defines the part and defines one surface of the bearing gap and has a first coefficient of expansion and a second element is wholly or partially inserted into and constrained within the first element and having a different coefficient of thermal expansion so that as the temperature changes, the stress created by the differential expansion of the two elements will cause the overall part to deform elastically as a function of temperature. This deformation will cause the gap, the elements being properly selected, to narrow as temperature rises (and viscosity falls) and to widen as temperature falls (and viscosity rises).

Abstract: A machine tool assembly, and particularly a spindle unit therefor, is provided wherein the spindle unit is relatively small and is designed to run at rotary speeds of between 30,000 rpm's and 40,000 rpm's utilizing hydrodynamic bearings for the spindle shaft. The hydrodynamic bearings are effective to take increased loads versus similarly sized conventional metal-to-metal contacting bearings to provide a very stiff machining system even with the higher loads generated by the increased rotary operating speeds for high speed machining contemplated for the spindle unit herein. The bearings are also designed to use a water-based fluid which is compatible with the cutting fluid. Non-contacting fluid barrier seals limit and control the amount of bearing fluid leaked to the cutting fluid. Due to the compatible nature of the two fluids, small fluid leakage from the bearings will not hurt the cutting fluid. The cutting fluid circulated at an ambient inlet temperature, e.g., 70.degree. F.

Abstract: A bearing assembly including a bering cone (50) having a crowned bearing surface (56) with V-shaped grooves (60) that are shallow at their apex (62) and deepest at the outer edges (52, 54). When mated with a female bearing seat, lubricating fluid builds up along the midline of the bearing surface as the bearing seat rotates about the bearing cone.

Abstract: In a seal or bearing that uses the tapered-sleeves-with-spiral-groove technology, the capacity is increased, without increasing the space envelope, by folding the tapered surfaces. Double and triple folding is illustrated. The seal/bearing may be used in e.g. a rotary impeller pump, or as a big-end bearing.

Abstract: An improved capillary seal for use with a hydrodynamic bearing is disclosed, which provides a stronger or stiffer seal for a fluid dynamic bearing motor which is open at both ends, and is used with top cover attached motors utilizing fluid dynamic bearings. The design for the seal system actively pushes the oil back into the FDB while it is spinning, combined with the capillary tension which holds oil in the FDB during stationary periods, and allows air, trapped within the seal and the associated FDB, to be expelled, eliminating air bubbles from the fluid dynamic bearing.

Abstract: A conical bearing apparatus is provided which is capable of enhancing productivity by reducing the time required for processing a hemispheric bearing i.e., grinding and lapping. By locating a spacer between a pair of cones, the cones are arranged on a fixing shaft facing each other and then inserted into a bush in which a pair of conical concaves for receiving the cones are formed. The thrust load and the radial load are supported by the dynamic pressure formed between the conical concaves and the dynamic pressure generating grooves formed on the tapered surfaces of the cones. Accordingly, as the bearing is conical shape, it is unnecessary to lap the hemispheric surface for minute clearance between the hemisphere and the hemispheric concave, thereby resulting in easy processing and enhancing the productivity of the bearing.

Abstract: A boring machine having a cutter head rotatably mounted on a hydrostatic bearing. High pressure water is supplied to passageways between confronting bearing surfaces which react axial and radial loads and which are capable of relative rotational movement. The flow of pressurized water discharges from the passageways to prevent contamination of the bearing by the ingress of material removed by the cutter head in operation.

Abstract: An integrated spindle and motor unit includes a housing containing both the spindle shaft and motor with hydrostatic bearings around the front and rear of the spindle shaft. The hydrostatic bearings utilize high pressure oil, preferably in the range of 1,200-1,500 psi and provide good load bearing capacity and increased stiffness for improved cutting accuracy when cutting within the full range of cutting speeds. The present spindle unit is designed to be run at high speeds. The front and rear hydrostatic bearing pads are closely axially spaced along the spindle shaft so that the dynamic stiffness of the spindle is increased to avoid resonant vibrations even at high speed operation thereof. The spindle unit incorporates a sealing system utilizing a series of non-contacting seals including a labyrinth seal and aerostatic floating ring seals which keeps bearing oil in the spindle.

Abstract: A conic fluid bearing includes a bush fixed to a rotary body. The bush has upper and lower portions on which conic cavities are opposingly formed, respectively. Upper and lower cones fit on a shaft fixed to a fixed body and are rotatably combined with said upper and lower conic cavities, respectively.

Abstract: A fluid bearing apparatus having an increased contact area between a body and a bushing and having a compact size. In the fluid bearing apparatus according to the present invention, a body extends from a shaft fixed to a lower bearing bracket in a lengthwise direction, which has a conical groove at one end and a truncated cone at the other end. An upper bushing includes a recess for receiving the one end of the body and having a conical protrusion formed therein. The conical protrusion is inserted into the conical groove of the body. A lower bushing has a recess receiving the other end of the body and a through hole extending through the lower bushing. The shaft is slidably inserted into the through hole. The upper bushing is separately combined with the lower bushing. Accordingly, the bushing which receives the body, may be decreased in volume, so that a motor to which the fluid bearing apparatus is applied, can be reduced in a total size.

Abstract: A conical bearing apparatus having a dynamic pressure generating groove on the upper section of a conical bearing in order to increase a fluid pressure generated by the other dynamic pressure generating groove formed on the tapered surface of the conical bearing. As fluid generated by the two dynamic pressure generating grooves is completely used for raising the body of rotation, it is possible to raise the body of rotation in a short time. Accordingly, the friction between an optical polygon support and the upper section of the conical bearing is minimized and an abrasion of the optical polygon support or the conical bearing can be reduced. Furthermore, by reducing the overload of the conical bearing and optical polygon support, the stability in rotating the optical polygon is enhanced.

Abstract: A rugged spindle for a disk certifier that test the disks of a hard disk drive. The spindle contains a first bearing and a second bearing that are coupled together by a shaft. The first bearing is coupled to a chuck that captures a disk. The second bearing is coupled to the spindle shaft of an electric motor which rotates the disk. The bearings each contain an outer graphite sheath that is separated from a hardened housing by an air bearing. The connecting shaft is bonded to the first and second bearings by an adhesive that is injected through longitudinal passages of the shaft. The bonding adhesive flows along the interface of the connecting shaft and bearings until the adhesive fills an indicator slot of the shaft. Air bearings are created during the bonding process of the second bearing to insure an accurate relationship between the two bearings and the housing.

Abstract: Radial and thrust bearing system with two hydrostatic bearings axially movable relative to a surrounding bearing housing. Each bearing includes a flange connected to the axle. The flange includes a pressure surface and a collar chamber bearing which has a surface facing the pressure surface and in it a collar groove, the surface and the pressure surface together forming internal and external tightening slots on either side of the collar groove. The pressure surface and the groove together forming a collar chamber to which hydraulic fluid is fed under pressure from a hydraulic fluid source. The collar chamber bearing with the bearing housing form a chamber that is put under hydraulic pressure for pressing the collar chamber bearing against the pressure surface, both collar chamber bearings being pressed in mutually opposite directions.

Abstract: A self-lubricating hydrodynamic spindle bearing comprising a stationary shaft including a conical, inwardly tapered surfaces extending axially form outer regions of the shaft toward a center connecting region of the shaft, a rotatably mounted sleeve surrounding the shaft and including surface regions flared axially inwardly toward a center region of the sleeve, the tapered surface regions and the flared surface regions defining a bearing gap for the hydrodynamic bearing, the sleeve defining a connection region adjacent the connecting region between the tapered surfaces of the shaft, the connection region including a tube collapsible in response to a change in internal pressure in the connection region to stabilize stiffness and power consumption in the bearing.

Abstract: A rugged spindle for a disk certifier that test the disks of a hard disk drive. The spindle contains a first bearing and a second bearing that are coupled together by a shaft. The first bearing is coupled to a chuck that captures a disk. The second bearing is coupled to the spindle shaft of an electric motor which rotates the disk. The bearings each contain an outer graphite sheath that is separated from a hardened housing by an air bearing. The connecting shaft is bonded to the first and second bearings by an adhesive that is injected through longitudinal passages of the shaft. The bonding adhesive flows along the interface of the connecting shaft and bearings until the adhesive fills an indicator slot of the shaft. Air bearings are created during the bonding process of the second bearing to insure an accurate relationship between the two bearings and the housing.

Abstract: A conical bearing system includes a first conical bearing having an integral shaft and a second conical bearing defining a bore having a shaft mating bore section and a threaded bore section. The system is assembled by applying adhesive to the shaft and inserting the shaft into the shaft mating bore section. A threaded screw is then screwed into the threaded bore section until the screw abuts the shaft. Then torque is applied to the screw to push against the shaft thereby causing the second conical bearing to move axially. Once the adhesive has cured, the screw may optionally be removed.

Abstract: A rotating assembly (10) comprises an inner (12) and an outer ring (14) having a hydrostatic bearing therebetween. The bearing incorporates fluid passageways (30 and 32) between confronting surfaces (22, 24, 26 and 28) of the rings (12 and 14). When rotation is required the surfaces (22, 24, 26 and 28) are separated by the supply of a pressurised flow of fluid to both of the passageways (30 and 32). The bearing can be locked to prevent rotation by removal of the fluid in one of the passageways (32) whilst maintaining the flow of pressurised fluid in the other passageway (30) so as to hold confronting surfaces (26 and 28) in contact with one another. Frictional forces between the confronting surfaces (26 and 28) prevents rotation of the ring (14) and the flow of pressurised fluid prevents the confronting surfaces (26 and 28) separating under the application of a moment.

Abstract: Non-axially-cylindrical journal and bearing assembly operates with hydrodynamic lubrication and has high load capability.

Abstract: A spindle and hub assembly in a disk drive having an integrated motor including a housing having a cylindrical sleeve and two end flanges, the cylindrical sleeve and the upper end flange being one piece and forming the hub and the lower end flange being pressed into the hub and a shaft being rotatably supported in the end flanges by means of hydrodynamic bearings, where the hydrodynamic bearings have conical bearing surfaces converging towards the interior of the housing, whereby a high precision and low cost spindle and hub assembly is provided.

Abstract: A hydrostatic gas bearing comprises a pair of bearing structural members 4 which make up an inner ring 3 and each have a frusto-conical engaging face 5 formed on the radially outer peripheral surface thereof, a pair of bearing members 2 which are fixed to the respective bearing structural members 4, and each formed with a radially inner engaging face 6 for engagement with the taper of the engaging face 5, and an outer bearing surface 10 which is aligned parallel to the inner engaging face 6, wherein since each bearing member 2 is pressed in an axial direction by an attachment member 7 and thereby fastened with a uniform pressing force to the bearing structural member 4, positional displacement of the bearing member 2 relative to the bearing structural member 4 and uneven deformation of the bearing member 2 can be suppressed so that bearing characteristics can be maintained in a simple structure.

Abstract: A bearing assembly has a load carrying housing subjected to oscillation that has an internal helical thread mating with a threaded load supporting stationary shaft, the threaded elements having seals at their ends for holding lubricant in the clearance space therebetween. In a preferred embodiment, one or more grooves are provided along the housing for the reception of debris and as a reservoir, additional clearance at the ends being provided for a lubricant reservoir.

Abstract: A bearing and a shaft and bearing combination for replacing conventional rolling element bearing, washer and lock ring assemblies. The bearing is constructed so that it can be precisely positioned with respect to the shaft in the housing. Additionally, the bearing provides both radial and thrust support so that the need for separate bearings is eliminated. The assembly is ideally suited for use in small high speed low load cooling fans used in computers, peripherals and other office equipment.The shaft includes a radially inward extending groove, preferably conically tapered. The bearing includes a base member, which can include a beam mounted radial bearing, and a number of longitudinal beams extending axially away from the base member. Each of the longitudinal beams supports a bearing pad in a cantilever fashion.

Abstract: A shaft support assembly particularly well suited for supporting the high speed rotor in a laser polygon mirror drive motor assembly. The rotor has conically tapered ends. These ends are supported by conical plain bearings. At least one of the bearings is adjustable with respect to the shaft and the bearing so that the gap between the shaft and bearing can be easily adjusted.

Abstract: A self-lubricating hydrodynamic spindle bearing for support of a spindle of a magnetic disk drive assembly includes a crankcase design which provides large reservoirs for oil storage with an air cover in communication with the ambient environment through an air vents provided by clearance seals formed between respective central passages of housing-sealing endcaps and the shaft. The crankcase reservoir volume is defined within the bearing so that natural body force effects cause the lubricant to be fed into the hydrodynamic bearing. A leak-preventing capillary trap of minimal continuous axial length may be provided at the clearance seal for passive capture of wandering lubricant when the bearing is at rest. Full evacuation of lubricant trapped at the clearance seal is achieved toward the interior of the housing by centrifugal pumping, e.g.

Abstract: An optical scanner has grease bearings between the rotor and the housing. The grease bearings are grooved which tends to pump the grease back into the bearing cups when the optical scanner is operating. The thixotropic property of the grease prevents its escape from the bearing cups when the optical scanner is not operating. The grease bearings can be frusto-conical or spherical in shape with complementary shaped bearing cups. The bearing cups, rather than the bearings, may be grooved. The bearing cups may also be stepped to provide a pumping region and a reservoir region for the grease. Pressure means within the scanner housing may force the bearing cups onto the grease bearing.

Abstract: An essentially completely and automatically self-adjusting fluid bearing assembly includes at least a front and rear bearing cone mounted for rotation with a driven shaft. Associated with each cone is a shell, such that a fluid gap exists between the shell and the associated cone. One of the shells, usually the rear shell, is held in place and biased by a spring or the like to urge the shell towards the associated cone to form the proper fluid gap while the other shell is provided with a differential diameter. Due to the differential diameter, the fluid pressure operates to urge the front shell towards the front cone thus keeping the fluid gaps in the proper fluid gap dimensions. Various structures are described.

Abstract: A fluid bearing assembly, e.g., air or gas, of the hydrostatic or hydrodynamic type, for use as a spindle and the like, includes spaced journals mounted on a shaft for rotation therewith. The housing includes spaced support bearings cooperating with the journals to form a gas gap therebetween. The support bearings are resiliently mounted in the housing for axial, radial and angular movement through the use of continuous resilient support elements positioned between the housing and the support bearings and continuously in contact with each. The resilient support elements are preferably self-energizing and comprised of relatively low coefficient of friction materials to reduce the friction of the system thus allowing rapid adjustment of the bearing in response to loads on the shaft. Various details are described with respect to the various structures illustrated, including the details of an air bearing spindle assembly of relatively light weight and capable of operating at speeds in excess of 100,000 RPM.

Abstract: A fluid bearing assembly, e.g., air or gas, of the hydrostatic or hydrodynamic type, for use as a spindle and the like, includes spaced journals mounted on a shaft for rotation therewith. The housing includes spaced support bearings cooperating with the journals to form a gas gap therebetween. The support bearings are resiliently mounted in the housing for axial, radial and angular movement through the use of continuous resilient support elements positioned between the housing and the support bearings and continuously in contact with each. The resilient support elements are preferably self-energizing and comprised of relatively low coefficient of friction materials to reduce the friction of the system thus allowing rapid adjustment of the bearing in response to loads on the shaft. Various details are described with respect to the various structures illustrated, including the details of an air bearing spindle assembly of relatively light weight and capable of operating at speeds in excess of 100,000 RPM.

Abstract: Herein disclosed is a particle processing apparatus to be used in a wide field including food, medical and chemical industries either for granulating or coating particles on a disk by rotating the disk in a barrel equipped with scrapers or for blending the particles in the barrel by rotating blades in the barrel. The particle processing apparatus comprises: a barrel for accommodating particles to be processed; a disk-shaped rotating member having an outer circumference of V-shaped section and including processing means for processing the particles in the barrel when the rotating member is rotated; rotating means for rotating the rotating member; and an annular bearing member having an inner circumference of V-shaped section for bearing the rotating member in a rotatable manner with a small gap between its inner circumference and the outer circumference of the rotating member.

Abstract: A gas bearing and shaft assembly includes complementary sets of guiding surfaces formed on the gas bearing and the shaft being mutually spaced apart defining bearing gaps therebetween, at least one guiding surface of each of the sets being a porous gas passage surface, a thin-porous layer adjoining the gas passage surface, a component having a given region disposed upstream of the gas passage surface in flow direction of gas fed under pressure through the component to the gas passage surface and the component having other porous gas-permeable regions, the gas passage surface and the thin porous layer together being denser than the other gas-permeable regions of the component producing a pressure drop at the thin porous layer being substantially greater than at the other gas-permeable regions, and gas outlet paths in communication with the bearing gaps within the bearing.

Abstract: Static pressure-type gas bearing for a high-speed rotary shaft, comprising a porous bearing bushing formed of a pair of hollow cone frustums connected to one another at respective narrow ends thereof.

Abstract: In an excavating machine having a lower frame, an upper frame and means for rotatably supporting the upper frame on the lower frame, an assembly for improving the load conditions of the upper frame supporting structure comprising an annular seal mounted on one of the upper and lower frames and disposed in wiping, sealing engagement with the other of the upper and lower frames, forming a sealed chamber between the upper and lower frames, and air is supplied under pressure to the chamber to provide an upwardly directed force on the upper frame alleviating the load imposed on the upper frame supporting structure.