Abstract:
A double-acting compressor to compress liquid or gaseous fluids includes a cylinder having a piston head that reciprocates between opposite ends of the cylinder; a fluid discharge and suction passages defined in at least one of the opposite ends of the cylinder; a fluid suction and compression chamber connected to each end of the cylinder; fluid suction and fluid discharge valves connected to each one of the opposite ends of the cylinder; and pulling device connected to each end of said piston head. The pulling device extends along the cylinder and project out of the ends of the cylinder. The pulling device includes at least one flexible string having fastening means for the manual operation of the compressor.

Description:
FIELD OF THE INVENTION 
     The present invention is directed to a compressor which can be used indistinctly to compress liquid or gaseous fluids, and more particularly to a single or double acting compressor defined by a cylinder in which a piston head or plunger is provided that can be manually reciprocated between two opposite ends of the cylinder, wherein on at least one of the longitudinally opposite ends one fluid inlet and one pressurized fluid outlet are defined. 
     It should be noted that, notwithstanding the fact that, in principle, this compressor was conceived and developed for use as a pump for bicycle tires and the like, providing the end-user with remarkable advantages as compared to conventional tire pumps, when put into practice with structural and dimensional adjustments appropriate to each application, it can be used as a universal compressor, for both home and general industrial applications. 
     BACKGROUND AND ADVANTAGES OF THE INVENTION 
     There are no known examples of prior-art compressors, whichever their application and operational capacity, with constructive and functional features providing the remarkable advantages of the compressor of this invention. However, by way of a simple comparative example, mention can be made of a known hydraulic compressor which transforms hydraulic energy into mechanical energy. Such compressor comprises two cylindrical bodies, aligned and connected to each other by their adjacent ends, having a sliding rod disposed therein, which has a compression head mounted on each of its opposite ends. Between each of the two heads and the corresponding opposite ends of the compressor a compressed gas chamber is defined, while a hydraulic fluid compression chamber is defined between the two heads along the adjacent portions of the cylindrical bodies. Reciprocation of the heads is caused by the injection and withdrawal of hydraulic fluid and causes the entry of gas and its subsequent discharge, after it has been compressed in the respective chambers, through respective valves located in both cylindrical bodies. Said heads comprise sealing piston rings spaced apart from each other, which define annular spaces between the cylindrical surface of each head and the matching inner surfaces of the cylindrical bodies. Said annular spaces define matching sealing chambers that prevent the passage of compressed gas into the compression hydraulic fluid chambers, wherein said sealing chambers of the heads comprise orifices communicating them with the corresponding compression hydraulic fluid chambers. Said orifices define inflow and outflow passages for pressurized hydraulic fluid, related to the forward and backward movements of the heads with respect to the gas compression chambers. 
     As it will be clearly explained below, the compressor of the present invention differs from the hydraulic compressor described above, in the first place, in the way it delivers displacement power to the piston, and also because of its remarkable simplicity of construction as compared to the complexity of the compressor of the prior art. While in the compressor of the prior art the source of driving power is hydraulic fluid which is working to achieve compression during the whole cycle, the operating force in the compressor of the invention is applied by means of flexible pulling strings or rigid rods fixed to a piston head, being the admission and compression chambers respectively defined on each of the sides of the piston head. 
     From the structural standpoint, the prior art compressor comprises two cylinders attached together, and a central wall therebetween which exerts reaction forces making the hydraulic fluid displace the piston, whereby the effective piston stroke is approximately half the total length of the cylinder. In the compressor of the invention, the effective piston stroke is practically equal to the total length of the cylinder; therefore, for the same cylinder length and diameter, the attainable compression ratio in the compressor of the invention is practically twice as much the ratio in the prior art compressor. 
     Additionally, it should be noted that the hydraulic compressor of the prior art will always requires a fluid compression pump, while the compressor of the invention, because of its versatility, will only need an external power source to run in high power systems, while in low power systems it can be operated manually with little effort. Contrary to the compressor of the prior art, the compressor of the invention was developed to obtain high yields of compression power with small pulling efforts exerted on a piston head by means of pulling elements fixed thereto. Since pulling efforts are easily achieved from the material and component geometry point of view, the weight and volume of the compressor can be reduced, which is an important advantage when the compressor must be transported in low weight, low power vehicles as is the case of bicycles. Additionally, when applying the pulling efforts to the piston head, preferably by means of flexible strings that project outside the compressor body, the strings can be oriented in many directions, Therefore, no extra space is required to operate the compressor as it should be the case when using, for example, rigid rods. The available space is fully utilized, and a high “available room/compression power” ratio is thus attained. However, as it has already been mentioned, in certain applications (for example in the industry), the use of rigid rods as traction means for the piston head may be appropriate. This is by no means a problem, since in this kind of application the available room is typically ample. Other differences and advantages will become apparent in the description of the compressor of the invention, where reference is made to the figures representing it in accordance with one of its preferred practical embodiments. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is a double-acting compressor that can be indistinctly used to compress liquid or gaseous fluids, said compressor being defined by a cylinder into which a reciprocating piston head is provided that can be displaced between two opposite ends of the cylinder, wherein in at least one of those cylinder ends, fluid discharge and suction openings are defined. Respective fluid suction and compression chambers are defined on both sides of the piston head, while respective fluid suction and discharge valves are provided at each of the opposite ends of the cylinder. The piston head is connected to tension members provided along the cylinder and projecting outwards from both opposite ends of the cylinder to cause the longitudinal reciprocating displacement of the piston head between the opposite ends of the cylinder. 
     It is a further object of the present invention a single-acting compressor that can be indistinctly used to compress liquid or gaseous fluids, such compressor being defined by a cylinder into which a reciprocating piston head or plunger is provided that can be displaced between the opposite ends of the cylinder, wherein a valve head is provided in a first end of the cylinder, said valve head comprising fluid suction and discharge openings, wherein a fluid suction and compression chamber is defined on one side of the piston head or plunger, wherein fluid suction and discharge valves are provided in a first end of the cylinder corresponding to such fluid suction and compression chamber, wherein a head defining an airtight cover is provided in said first cylinder end, wherein said plunger is connected on one side to traction means projecting out of the cylinder for the manual operation of the compressor, and connected on the other side to elastically-deformable traction means extending between said plunger and a second cylinder end, said cylinder being open to allow for the free displacement of the plunger, said traction means being capable of expanding elastically and allow for the displacement of the plunger to effect the compression and discharge of the fluid, and also capable of contracting to force the return of the plunger, thereby suctioning the fluid into the fluid suction and compression chamber. 
     According to one of the preferred embodiments of the invention, the compressor, either of the single-acting or double-acting type, can be fixed to one of the members of a bicycle frame, as an integral part of said bicycle frame, in which case the compressor is a tire pump. In another preferred embodiment of the invention, the compressor can be attached below the bicycle seat by the head in the first cylinder end, thereby forming the seat post that is housed into the seat tube. In the latter case the compressor is also a tire pump that forms an integral part of the bicycle. In the second embodiment, the seat tube must comprise an orifice to allow for the passage of the discharge valve nozzle, to which the air hose carrying the air to the bicycle tire should be connected, as well as another opening for the suction of air through the suction valve. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       For the sake of clarity and understanding of the object of the invention, it has been represented in its preferred exemplary embodiments, which are illustrated in the following figures: 
         FIG. 1  is a general perspective view of the compressor of the invention according to a first embodiment. 
         FIG. 2  illustrates schematically a side view in partial longitudinal section of the compressor of  FIG. 1 . 
         FIGS. 3 to 6  are partial views in longitudinal section of the compressor of  FIG. 2 , illustrating the operation of the compressor. 
         FIG. 7  is a longitudinal section view of a second embodiment of the compressor. 
         FIG. 8  is a partial perspective and longitudinal section view of the compressor of  FIG. 7 . 
         FIG. 9  is a partial perspective view of the upper end of the compressor of  FIG. 7 , from which it is fixed to a bicycle seat. 
         FIG. 10  is a perspective view showing the compressor of  FIG. 7  fixed to a bicycle seat. 
         FIG. 11  is a side view of a bicycle with the compressor according to the embodiment of  FIG. 1 . 
         FIG. 12  is a side view of a bicycle with the compressor according to the embodiment of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Starting with the description of  FIGS. 1 and 2 , it can be appreciated that this double-acting compressor comprises a cylinder  1  which opposite ends have first and second suction valves  2  and  3  respectively for the fluid to be compressed, as well as a first and a second pressurized fluid discharge valves  4  and  5  respectively. The discharge valves  4  and  5  are interconnected by means of a manifold duct  6 , through which the compressed fluid to be used during one of the suction-compression cycles is pumped from valve  5  to valve  4 . As will be described later, since both suction valves  2  and  3  and discharge valves  4  and  5  are of the check valve type, in each compression cycle one of the suction valves stays open while the other stays closed, and, similarly, while one of the discharge valve stays closed the other stays open. 
     Within cylinder  1  (see  FIG. 2 ) is provided a piston head  7  that reciprocates between the opposite ends of the cylinder that is between the vicinities of the corresponding suction and discharge valves during the operation of the compressor. On both sides of the piston head  7 , corresponding fluid suction and discharge chambers are defined, which mutual tightness is guaranteed by means of annular rings  7   a  y  7   b . In order to displace the piston head  7  along cylinder  1  alternatively in both directions to effect the suction/compression operations, the piston head is connected to pulling means extending along said cylinder  1  and projecting out of the cylinder from both opposite ends thereof. Said pulling means of piston head  7 , depending on the specific application of the compressor, can be define either by a rigid rod or by a flexible string. In the preferred embodiment described herein, said pulling means comprise a flexible string  10  comprising a section  11  placed within the suction/compression chamber  8  and another section  12  placed in the suction/compression chamber  9 , as well as sections  14  and  15  projecting out of the cylinder  1 . In order to attach firmly piston head  7  to each of the sections  11  and  12  of the flexible string  10  during the operation of the compressor, said string  10  is fastened to each side of piston head  7  by means of corresponding adjusting fasteners  13 . 
     Since in the exemplary embodiment described herein the compressor is operated manually, sections  14  and  15  projecting out of the compressor from the opposite ends thereof, passing through corresponding essentially tubular pieces that define tightness seals  16  and  17  for the suction/compression chambers  8  and  9  of cylinder  1  against the surrounding atmosphere, end in corresponding holding means for the end user, which comprise handles  18  and  19  (see  FIG. 1 ). On each end of the compressor corresponding grooved wheels  20  and  21  are arranged, which define a guide for the outward projection of sections  14  and  15  of string  10 , so that the string will slide easily when the end user alternatively pulls from handles  18  and  19  to effect the reciprocating movement of piston head  7  along cylinder  1 . 
     It should be mentioned that when the pulling means of piston head  7  comprise a rigid rod, such rod can also be fitted with handles or, if applicable, a member capable of connecting the rod to a driving mechanism, such as when the compressor is of dimensions and capacity suitable for industrial use. This situation is also valid for the case where the pulling means are flexible strings. 
     The suction valve  2  comprises openings  44  for the inflow of suction fluid into a chamber  22 , and further into the suction/compression chamber  8  through a fluid passage  23 . In said chamber  22  a valve mechanism of the “clap” type is arranged, which is defined by a disk  24  and an expansion spring  25 . During the suction cycle by means of valve  2  (see  FIGS. 3 and 4 ), the displacement of piston head  7  exerts a suction force enough to overcome the expansion force of spring  25 , thereby allowing the suction of fluid through openings  44 ; the fluid then passes through passage  23  and reaches chamber  8 . On the other hand, discharge valve  5  comprises a discharge chamber  39  where a valve mechanism of the “clap” type is arranged, which is defined by a disk  41  and an expansion spring  42 . The compression of the fluid exerted by piston head  7  in chamber  9  creates a force strong enough for the fluid to reach openings  40 , communicating said chamber  9  with chamber  39  in valve  5 , overcomes the expansion force of spring  42  and, consequently, the fluid enters into said chamber  39 , passes through passage  43 , flows along duct  6 , passes through passage  45 , and enters into chamber  26  in the discharge valve  4 . If openings  29  are closed by disk  27 , the fluid is pumped under pressure, through the opening  30 , into hose  32 , which is connected to the discharge nozzle  31 , to inject the pressurized fluid into where the compressor end user needs to. As shown in  FIG. 4 , during the fluid suction cycle into chamber  8  and compression into chamber  9 , the suction valve  3  stays closed under the expansion force of spring  38 , with the additional contribution by the pressure of the fluid arriving into chamber  35  through passage  36 . 
     Optionally, in the practice, discharge valve  5  can be made to be identical to discharge valve  4 , i.e. comprising a fluid discharge port and a nozzle (not shown), similar to those described with reference numbers  30  and  31 , to connect the other hose, such as hose  32 . Thus, during the compression cycle in chamber  9  of cylinder  1 , pressurized fluid will be made available at the discharge port of both valves  4  and  5 , which in turn will allow to, for example, pump compressed fluid simultaneously into the chambers of the two wheels in a bicycle, or wherever it would become necessary according to each particular application of the double-acting compressor of the invention. 
     A variation of this first embodiment, which is not considered necessary to be illustrated herein, consists in adapting the compressor to work as a “simple-acting” compressor. That is, the compressed fluid will be pumped, for example, only through discharge valve  4 , to which hose  32  is connected. To obtain this it is only necessary to remove duct  6  and shut passage  45  of valve  4 , and leaving passage  43  of valve  5  open to allow for venting of the fluid, in this case gas or air, reaching said valve  5 . Optionally, valves  3  and  5  could be dispensed with, leaving a venting opening where valve  3  and/or  5  used to be. 
     Additionally, depending of the various possible applications of the compressor of the invention, for example as a pump for bicycle tires and the like, or as a compressor for industrial use, it is possible to take advantage of the concept of “relative motion” between the compressor body and the piston head  7 . That is, either keeping the compressor body fixed while displacing the piston head  7  or, conversely, displacing the compressor body while piston head  7  is kept fixed. In order to obtain this in a simple way, sections  14  and  15  of string  10  (or, if applicable, the rigid rod used instead) should be fastened to their corresponding fixing points, and coupling the compressor body, for example, from cylinder  1  or another convenient point, to displacement means of the compressor body. Such displacement means can be the handle used for the manual operation of the compressor, or a suitable driving mechanism with the same purpose. 
     In another alternative embodiment that can be put into practice, at least one of the sections of the flexible string  10  is hollow and defines a discharge duct for the pressurized fluid, either additional to hose  32  or for individual use. Similarly, hollow rigid rods could be used as traction means for the piston head and also to conduct the pressurized fluid. 
     In the exemplary embodiment described herein, it is shown that the discharge end of hose  32  is coupled to a tire pump nozzle  33  (see  FIG. 1 ), such as those frequently used to inflate bicycle tires. However, as it will be readily understood, this is just one of the various application examples for the compressor of the invention. 
     As shown in  FIGS. 5 and 6 , during the compression cycle of piston head  7  in chamber  8 , the operation of suction valves  2  and discharge valves  4  (which has been explained hereinabove), is supplementary, or inverse, with respect to the operation of suction valves  3  and discharge valves  5 , which are structurally and operatively linked to the suction/compression chamber  9  of cylinder  1 . Suction valve  3 , in the same manner as suction valve  2 , comprises openings  34  for the suction of fluid into chamber  35 , from which the fluid passes to the suction/compression chamber  9  through a fluid passage  36 . In said chamber  35  a valve mechanism of the “clap” type is also arranged, which is defined by a disk  37  and an expansion  38 . During the suction cycle, the displacement of piston head  7  exerts a suction force strong enough to overcome the expansion force of spring  38 , thereby liberating the suction of fluid through openings  34 , then flowing through passage  36 , and reaching chamber  9  in cylinder  1 . The same suction force is added to the expansion force of spring  42 , thereby contributing in keeping disk  41  in discharge valve  5  in a shut position regarding openings  40 . In this situation, that is, while chamber  9  is in the suction cycle, chamber  8  is operating in the compression cycle and, therefore, the fluid flows through opening  30  of the discharge valve  4 , and is pumped under pressure towards hose  32 . 
     Summing up, in this exemplary embodiment, when the end user pulls sections  11  and  12  of string  10  by means of handles  18  and  19  in a reciprocating fashion, he causes the displacement of piston head  7  in one or the other direction along cylinder  1 , thus creating alternate fluid suction and compression cycles in chambers  8  and  9 . In this way, when the user pulls from section  14  of string  10 , piston head  7  creates a suction cycle in chamber  9  and a compression cycle in chamber  8 , keeping suction valve  3  open, discharge valve  5  closed, suction valve  2  closed, and discharge valve  4  open. Conversely, when the user pulls from section  15  of string  10 , piston head  7  creates a suction cycle in chamber  8  and a compression cycle in chamber  9 , keeping suction valve  2  open, discharge valve  4  closed, suction valve  3  closed, and discharge valve  5  open. Consequently, in each fluid suction/compression cycle in chambers  8  and  9 , when corresponding, the fluid is always caused to traverse chamber  26  of valve  4  and is forced under pressure towards hose  32 . 
     A preferred application form of the compressor according with this first embodiment is shown in  FIG. 11 , where the compressor is shown, which in this example it defines a tire pump, is fastened to a bicycle frame as an integral part thereof. Sections  14  and  15  of string  10  with handles  18  and  19  are not shown here for the sake of simplicity. 
     In  FIGS. 7 to 10  show an additional embodiment of the compressor of the invention, now as a single-acting compressor, comprising a cylinder  46 , within which, one side of piston head or plunger  47  defines a chamber  48  of fluid suction and compression, and in a first end  49  of the compressor, adjacent to said chamber  48  of suction and compression, a fluid suction valve  50  and a fluid discharge valve  51  are arranged, comprising a nozzle  51   a  to which a hose is connected, this hose conducts the pressurized fluid to inject it into, for example, a bicycle tire, this application being one of the uses foreseen for the compressor of the invention. 
     Plunger  47  is connected, on one side, to pulling means defined by a thin flexible string  52  projecting out of cylinder  46  for the manual operation of the compressor, and on the other side to pulling means defined by an elastically deformable string  53  extending between plunger  47  and a second open end  54  of cylinder  46 , which allows for the free displacement of plunger  47 . In the elastically deformable string  53 , which is preferably folded on itself forming two sections, a first end  55  attached to plunger  47 , and a second end  56  attached to a string fastening bolt  57  provided in end  54  of cylinder  46 . The elastically deformable string  53  is capable of expanding under longitudinal traction and allow plunger  47  to advance so to compress and discharge the fluid, and can also contract, when the pulling force is released, so to force plunger  47  to retreat and allow for the suction of fluid into fluid suction and compression chamber  48 . 
     At end  49  of the cylinder a head  58  is provided that defines a tight cover including housings for fluid suction and discharge valves  50  and  51 , and the pulling string  52  projects out of cylinder  46  through a opening in said head  58 , terminating in a user-operable end where a traction handle  59  for the manual operation of the compressor is arranged. Head  58  comprises a tubular piece  60  made of elastic material, defining a tight passage for the pulling string  52 , and a grooved wheel  61 , rotatably mounted on a shaft  62 , thus defining a guide for the displacement of said pulling string  52 . 
       FIG. 10  illustrates one of the exemplary uses of the compressor according with this second embodiment, where it is possible to appreciate that cylinder  46  is fixed to seat  63  of a bicycle through head  58  placed at end  49  of cylinder  46  (see  FIG. 12 ), thereby forming the seat post housed inside the seat tube, which serves to attach seat  63  to the bicycle frame. Head  58  comprises a pair of openings  65  for the passage therethrough of screws to attach the compressor to the base of seat  63 . In this way, the compressor comprises a tire pump as an integral part of the bicycle frame. The seat tube  64 , or an extension thereof, or a part of the bicycle frame connecting with the open end  54  of cylinder  46 , should comprise at least one opening connecting with the surrounding atmosphere, to allow for free air suction and discharge, so that plunger  47  can easily move back and forth, that is, without being affected by vacuum or air pressure accumulating in the bicycle frame. 
     The compression cycle starts by displacing plunger  47  towards the end  49  of cylinder  46 , where the head  58  is attached, by means of the pulling force exerted by flexible string  52  from handle  59 . When plunger  47  advances, it compresses the fluid in compression chamber  48 , suction valve  50  closes, discharge valve  51  opens, and the compressed fluid is discharged through nozzle  51   a , and runs along  66 , with its corresponding fitting  67 , which has been connected to said nozzle  51   a  to inject compressed air into the bicycle tire that needs to be inflated. During such displacement of plunger  47 , the elastic string  53  stretches and accumulates contraction energy. After the compression cycle is finished, plunger  47  is liberated by stopping to pull from handle  59 , then the flexible string  52  becomes loose, and the elastic string  53  contracts until finally reaching its rest state, returning plunger  47  to its initial position. When plunger  47  starts its return movement, it creates vacuum in the compression chamber  48 , thereby closing discharge valve  51  and opening suction valve  50 , thus allowing the suction of air into the compression chamber  48 , and leaving the compressor ready to start a new operation cycle.