Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D33/00—Non-positive-displacement pumps with other than pure rotation, e.g. of oscillating type

Definitions

• the invention relates to pumping devices for air or liquids and specifically to a blower utilizing an undulating blade.
• Electronic equipment is customarily cooled using rotary fans or blowers, which circulate air through the entire housing to maintain a constant operating tempera ⁇ ture.
• Steady state temperature maintenance of the electronic components is important not only to prevent overheating, but also to assure reliable operation.
• the present invention is a revolutionary solid state blower of the -undulating blade type which is extremely efficient, inexpensive to manufacture, and designed for a long service life.
• the present invention is a pumping device which may be used to pump gases or liquids having a housing and an elongated impeller or blade mounted to the housing and free to move laterally.
• a piezo ⁇ electric bending element, or so-called “bilaminate” is mounted at one end on the housing, and on its other end supports the blade ' to apply a sinusoidal driving force to the blade for propagating a traveling flexure wave along the blade, preferable in a quadrature rela ⁇ tion, thereby to pump the gas or liquid.
• the entire length of the blade is free to move laterally as it is driven back and forth by the piezo- electric element.
• the blade may be contained in a pumping duct or channel in the housing so that the blade motion itself provides inlet and outlet valving.
• the piezo-electric bilaminate is a strip consisting of two layers of piezo-electric ceramic, polarized in opposite directions, which on their facing sides are separated by a conducting layer and which on their outside faces are surrounded by conducting layers.
• the two outside conducting layers are connected as electrodes to a controlled alternating current supply. Since the piezo-electric layers have opposite polarity, voltage applied across the bilaminate strip induces bending of the element. Accordingly, alternating voltage across the piezo-electric element will drive the blade back and forth at the point of attachment.
• the blade material, resiliency, taper, and width are preferably selected to tune the impeller to the oscillating frequency of the drive arrangement to result in stable and efficient operation.
• the blade may be driven at two or more points, in which case these considerations become less critical, and high efficiency can be attained at other than resonant frequency.
• the blower operates without any substantial mechanical friction to permit high operating speed, a consequently high throughput relative to size, a virtually unlimited service life, and may be miniatur- ized and still produce a significant flow of air to cool miniature components.
• the device In its miniaturized form, the device may be mounted directly on printed circuit boards, alongside the individual components which require cooling, and due to its high efficiency will provide sufficient cooling air.
• the blower preferably is constructed with a pair of counter-oscillating blades in parallel pumping channels so that it is dynamically balanced and vibration free. Pumping efficiency of the device may be improved by providing venturi intake ports along the output half of the duct to increase the air flow through the ducts.
• Fig. 1 is a pictorial view of a solid state blower having a pair of blades driven by piezo ⁇ electric elements according to the invention
• Fig. 2 is a longitudinal-sectional view of a piezo-electric bilaminate driving element for use with the blower of Fig. 1;
• Figs. 3a, 3b, 3c, 3d, 3e and 3f are schematic representations of first the blade at rest and then the pumping motion of the blade, phased in quadrature, at various points of the oscillation cycle;
• Fig. 4 is a pictorial view of a modified form of the solid state blower shown in Fig. 1.
• a solid state blower according to the present invention has a housing 10, outer walls 12 and an inner divider 14 forming a pair of air channels 16 between the bottom 17a and top 17b (lifted* out of the way for clarity).
• a pair of resilient blades 18 are mounted in the channels 16 for driving air through the device.
• the blades 18 are generally tapered from their inlet ends 24 toward the outlet ends 22 and have whip portions 20 at their outlet ends 22 to improve the air throughput pumping capacity.
• the whip portions 20 are preferably made of Mylar.
• a piezo-electric bilaminate 28 is attached at one end 40, for example by a plastic holder and screws 41, to each of the housing walls 12 and at the other end 42, by cementing or any other suitable means to a point on each blade 18 to support the blade in the channel 10 in a manner such that upon lateral movement of the bilaminates the blades 18 are free to undergo simul- taneous lateral deflection. " This mounting arrange ⁇ ment permits free lateral movement of the blade 18 along the entire length with corresponding lateral movement of the end 42 of the piezo-electric element 28.
• a piezo-electric element suitable for use in the present invention is marketed by Gulton Industries, Inc., Piezo Products Division, Metuchen, N.J., under the name "Piezo Ceramic Bender Element", No. G1195.
• Each bi ⁇ laminate strip 28 (Fig. 2) has two layers of piezo- electric ceramic 29 separated by a layer of conducting material 30, e.g. brass.
• the outside layers 32, 34 are silver, and connected to the leads 36, 38 of a controlled alternating current supply 39.
• the two ceramic layers 29 are polarized in opposite directions, so that voltage across the bilaminate induces a bending motion in the strip.
• bilaminate strip 28 Since the bilaminate strip 28 is fixed on the housing at 41, controlled alternating voltage, therefore, causes the free end 42 of the piezo-electric element 28 to move back and forth at the voltage frequency. The bending movement of the bilaminates 28, in turn, drives the blades 18 back and forth at the point of attachment 42 at a controlled rate.
• connections from the piezo-electric elements 28 to the power supply 39 are conveniently made at the end 40, beneath the holder 41.
• the blade 18 When driven back and forth, the blade 18 represents a beam subjected to combined bending and shearing loads varying so rapidly that inertial effects dominate to propagate a traveling flexure wave along the impeller or blade from the inlet end of the duct toward the outlet end of the duct.
• a voltage oscillating in the range of 60-400 hz is applied.
• the most efficient pumping action results when the driving force is applied in quadrature, that is, to produce a 90 degree ( ⁇ ) phase lag in the oscillation cycle between two points along the blade, for example near the inlet end of the duct and near the outlet end, as illustrated schematically in Figs. 3a-3f.
• the driving force (F) is applied at a single point, and with a selected frequency range ' depending, e.g., upon the blade material, taper, and resiliency and thus the blade resonant frequency, such that the blade undergoes both lateral displacement and bending at the point of applied force.
• the driving force F on the blade produces the successive blade shapes shown in Figs. 3a-3f and directions of air motion (A) indicated by arrows, as described below.
• the blade may be operated either in a free medium or in a duct, e.g. 16.
• the duct 16 has a width such that the ends 24, 22 of the blades 18 contact, or almost contact, the duct walls, during the back and forth lateral movement, the down ⁇ stream contact lagging the upstream point of contact by 90° of the oscillation cycle.
• the two contact points will have a quadrature relation with respect to each other so that the blade tips perform the functions of intake and outlet valves. See Figs. 3b-3f.
• Air throughput is also improved if venturi air louvers 56 are provided in the duct walls in the output half of the blower.
• the blower contains two counter-oscillating blades 18 to operate 180° out of phase with each other.
• the complementary back and forth motion of the two blades 18 provides dynamic balancing and prevents vibration of the device.
• the device is very efficient, and in tests, operation has been very stable, with efficiency so high that rises in temperature of the bilaminates have been virtually undetectable.
• FIG. 4 A modified embodiment of the solid state blower illustrated in Fig. 1 is shown in Fig. 4, where in place of the side mounted piezo-electric element 28, a pair of end-mounted bilaminate piezo-electric elements 128 drive respective ones of a pair of flat resiliant blades 118. The free ends of the blades are terminated in whip portions 122, preferably made of Mylar.
• the blower assembly includes a housing 110, side walls 112 and a bottom plate 117a.
• a top cover may be added if desired, similar to cover 17b shown in Fig. 1.
• the blades 118 are not disposed in separate pumping ducts, yet efficient pumping action is achieved without the enhanced valving action produced by the ducts due to the quadrature travelling wave induced in the blades 118.
• the piezo-electric bilaminates 128 are mounted at one end 140 to a cross member 141 bridging the walls 112 of the housing 110.
• the member 141 is provided with a pair of vertical slots 142, each of which is sized to snugly receive the end of the bilaminate 128 and a pair of electrically conductive contact leaves 144, one on either side of the bilaminate. Conductors, not shown, are connected to the leaves for coupling to the alternat ⁇ ing voltage supply.
• the free ends of the bilaminates 128 are attached to coupler weights 150, which in turn support the resilient blades 118.
• the weights 150 have vertical slots along their narrow edges for snugly engaging the bilaminates and blades, respectively. As shown in Fig. " 4, the blades preferably are substantially wider than the bilaminates, to maximize air flow.
• the blade 118 is not fixed at any point relative to the housing and is free to move laterally (i.e., perpendicular to the flat surface of the blade 118) back and forth along its entire length when driven by the free end of the piezo-electric element 128.
• the blower works very efficiently in pumping fluids, especially air, without the need for blade valving action.
• the two bilaminates are driven to opposing phase relationship, as in the Fig. 1 embodiment.
• both Figs. 1 and 4 can provide effective air movement with a single oscillat- ing blade.
• the blade may be driven at two or more points along its length, in which case the resonant frequency and driving frequency become less of a factor in determining efficiency. All such modifications and variations are intended to be within the scope of the invention as defined in the following claims .

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)

Applications Claiming Priority (4)

Publications (3)

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Country Status (4)

Cited By (2)

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• 1980
  • 1980-05-06 JP JP50125980A patent/JPS6315480B2/ja not_active Expired
  • 1980-05-06 WO PCT/US1980/000534 patent/WO1980002445A1/en active IP Right Grant
  • 1980-05-06 DE DE8080901052T patent/DE3067101D1/de not_active Expired
  • 1980-11-17 EP EP80901052A patent/EP0028245B1/de not_active Expired

Non-Patent Citations (1)

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