Abstract:
The disclosure relates to a device for pressurising a fluid to be combined with a rotary power takeoff of a vehicle including a casing and at least one multiplication stage, the device including a frame bearing at least one first rotatably moveable shaft bearing a member for moving the fluid and dynamic coupling means for coupling the shaft to the power takeoff. The frame includes means for bearing and attaching to the casing and the coupling means are arranged so as to directly connect the mobile shaft to the multiplication stage of the power takeoff. The disclosure also relates to a device for pressurising a fluid, including a frame, rotatably moveable first and second shafts each bearing a member for moving the fluid, and dynamic coupling means for coupling the first or second shaft to the power takeoff, including a removable pinion that can be alternately mounted on the first or second shaft. Finally, the disclosure also relates to a system including a power takeoff and to a device for pressurising a fluid.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a National Stage Entry of International Application No. PCT/FR2008/001808, filed on Dec. 19, 2008, which is incorporated by reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to a fluid pressurizing device, to be mounted on a power take-off of a motor vehicle and to a system including a power take-off and such a pressurizing device. The invention more particularly relates to compressors and pumps connected to a power take-off of a motor vehicle. 
       BACKGROUND 
       [0003]    In the prior art, fluid pressurizing devices, such as pumps or compressors, which are associated to the power take take-off of a motor vehicle are known. The power take-offs are generally fixed on a gear box and take their rotational movement on one of the pinion gears of said gear box. The power take-off comprise an output sleeve for transmitting the movement to a driveshaft and, usually, a steering clutch, separated from the main clutch of the vehicle for connecting or disconnecting the gear box at the power take-off output side. The power take-off can further include a speed multiplication between the input speed and the output speed. The reduction or multiplication ratios commonly range between 0.5 and 2. 
         [0004]    The pressurizing devices comprise at least a frame and one or two rotatable shafts, bearing a member for pressurizing the fluid, such as a pump or compressor. Usually, the frame of the pressurizing devices is assembled on the vehicle body and a Cardan joint driveshaft, connected on the one hand to the power take-off and on the other hand to the pressurizing device makes it possible to impart the movement of the power take-off to the pressurizing device. 
         [0005]    In some cases, and on the particular case of screw compressors, the output speed of a power take-off is not sufficient to drive the compression members at the needed speed. Consequently, a multiplier is embedded to the compressor. Indeed, the rotational speed on the outlet side of the power take-off can reach only about 2000 rotation/min whereas the speed necessary for a screw compressor to correctly operate is higher than 10000 rotation/minute. 
         [0006]    In addition, the pressurizing devices comprise a safety device for limiting the torque transmitted between the power take-off and the movable member providing the pressurization of a fluid. Indeed, in the case where the compressor or the pump is blocked, it is necessary to limit the torque transmitted to avoid the breakage of the transmission members. Consequently, the devices of the prior art exhibit a high encumbrance, because of the presence of a multiplier and a torque limiting device, so that the integration of these devices to a motor vehicle is not satisfactory. Moreover, the installation of these devices is complex because they must be fixed beforehand to the vehicle body, then connected to the power take-off by the Cardan joint driveshaft. 
         [0007]    In addition, patent application WO 2007/0589594 discloses a device comprising a hydraulic pump in a housing which is removably assembled to the power take-off. However, in the case of high power pressurizing devices, and consequently exhibiting big sizes and weights, this solution is not satisfactory because the present weights generate too important loadings at the junction between the power take-off and the gear box. Thus, this solution is not satisfactory either. 
         [0008]    Moreover, depending on the manufacturers, the rotation direction at the output side of the gear boxes, and thus at the outlet side of the power take-off, may be clockwise or anticlockwise. Thus, in the prior art, either, as a standard, the fluid pressurizing devices are adapted to one rotation direction or the other, or a rotation inverter is disposed between the power take-off and the device. The first solution causes the manufacturers to have two different device references whereas the second solution increases the encumbrance and the complexity of the system. 
       SUMMARY 
       [0009]    The aim of the invention is to remedy to these problems by providing a fluid pressurizing device to be associated with a rotary power take-off, which is reliable and whose encumbrance and integration on the motor vehicle are satisfactory. To this end, and according to a first aspect, the invention provides a fluid pressurizing device, to be associated with a rotary power take-off of a motor vehicle including a casing and at least a multiplication stage, said device comprising a frame supporting at least a first rotatably movable shaft bearing a member for moving the fluid and dynamic coupling means for dynamically coupling the shaft to the power take-off. The device is remarkable in that the frame comprises means for bearing and attaching to the casing of the power take-off and in that said coupling means are arranged to directly connect the mobile shaft to the multiplication stage of the power take-off. 
         [0010]    Thus, the integration and the attachment of the device are satisfactory because the frame of the device is attached and supported by the casing of the power take-off. Moreover, the dynamic coupling means directly connect the mobile shaft, bearing the fluid moving member, to the power take-off. Thus, the pressurizing device does not comprise a multiplier because it is off-set in the casing of the power take-off. 
         [0011]    Thus, the load related to the multiplier is brought closest to the junction between the power take-off and the gear box so that the device, thus made up, is more compact, lighter and consequently, the system composed of the device and the power take-off becomes compatible with the permissible loadings at the junction between the power take-off and the gear box. To note that what is meant by “direct” connection between the mobile shaft and the multiplication stage of the power take-off, is the fact that the coupling means comprises a single transmission element between the multiplication stage and the mobile shaft. In other words, the device does not comprise a multiplication stage, other than that of the power take-off. 
         [0012]    Advantageously, the coupling means comprise a pinion borne by the first mobile shaft. This coupling means allows a direct cooperation with the output pinion of the power take-off. The driving of these pinions allows a multiplication of the rotation speed. 
         [0013]    In one embodiment, the attaching means comprise a peripheral mounting flange, to be disposed against the casing of the power take-off. Advantageously, the mounting flange comprises a cradle shaped portion for allowing the passage of the multiplication stage of the power take-off. Advantageously, the attaching means comprise centering and positioning means. These means make it possible to secure a precise dynamic coupling between the device and the power take-off. 
         [0014]    Advantageously, the transfer device comprises an internal lubricating circuit and means for connecting the internal lubricating circuit to the motor vehicle lubricating circuit. Indeed, in some particular cases, the rotary members of the device may require a forced lubrication. The invention meets this requirement by providing a lubricating circuit to be connected to a lubricating circuit of the motor vehicle including pumping means and disposed, for example, in the casing of the power take-off. Thus, the weight and the encumbrance of the pumping means of the lubricant and the lubricant tank are supported by the motor vehicle, in particular by the power take-off, so that the encumbrance and the weight of the pressurizing device are little affected by the lubricating means. In a preferred embodiment, the connecting means comprise a supply opening extending in the axis of rotation C of the power take-off multiplication stage so as to allow a supply of the lubricant by the support shaft of said multiplication stage. This solution is particularly compact. Moreover, the internal lubricating circuit comprises a filter. 
         [0015]    According to a second aspect, the invention relates to a fluid pressurizing device to be associated with a rotary power take-off of a motor vehicle including a casing, said device comprising a frame, a first and second rotatably movable shafts each bearing a member for moving the fluid, means for synchronizing the rotation of the first and second shafts arranged to drive the first shaft along a first rotation direction and the second shaft along a second rotation direction in a suitable speed ratio; and means for dynamically coupling the first or the second shaft to the power take-off. The device is remarkable in that said coupling means comprise a removable pinion to be mounted either on the first or on the second shaft, depending on the rotation direction of said power take-off, so as to drive the first shaft along the first rotation direction and the second shaft along the second rotation direction, regardless of the rotation direction of said power take-off. 
         [0016]    Thus, the device according to the second aspect of the invention may fit to the various gear boxes and power take-offs available on the market. Moreover, this adaptation is simple and does not require an additional adapter which would increase the weight and the encumbrance of the device, so that this solution is particularly interesting when the device frame is attached and supported by the casing of the power take-off. Moreover, the synchronization means advantageously has a multiplication ratio of about 1.2. Finally, the invention relates to a system comprising a rotary power take-off including a casing and a fluid pressurizing device according to the first and/or the second aspect of the invention, associated with said casing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    Other objects and advantages of the invention will become more apparent from the following description, made with reference to the accompanying drawings, wherein: 
           [0018]      FIG. 1   a  is a perspective view of a pressurizing device according to the invention, cooperating with a movement transmission pinion of the power take-off; 
           [0019]      FIG. 1   b  is a perspective view of a system comprising a pressurizing device and a power take-off, the casing of which is to fixed on a gear box; 
           [0020]      FIG. 2  is detailed perspective view of the pressurizing device of  FIG. 1   a;    
           [0021]      FIG. 3  is a front view of a device according to the invention illustrating the means for bearing and attaching the casing; 
           [0022]      FIG. 4  is a perspective view of a device according to the invention comprising centering and positioning means according to a second embodiment; 
           [0023]      FIG. 5  is a perspective view of a device according to the invention, illustrating the means for connecting the internal lubricating circuit to a lubricating circuit of the motor vehicle; 
           [0024]      FIG. 6  is a view of the device of  FIG. 5 , cut along plan VI-VI; 
           [0025]      FIG. 7  is a view of the device of  FIG. 5 , cut along plan VII-VII; 
           [0026]      FIG. 8  is a cross-sectional view of the device of  FIG. 5 ; 
           [0027]      FIG. 9  illustrates a system according to the invention comprising a power take-off and a pressurizing device, mounted on a gear box; and 
           [0028]      FIGS. 10 ,  11  and  12  illustrate a device according to a second embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    The fluid pressurizing device represented in  FIGS. 1 to 11  is a screw compressor  1 . Compressor  1  is to be associated with a power take-off  2  of a motor vehicle, represented in  FIGS. 1  b and  10 . The power take-off  2  comprises a casing  3  which is to be attached on the gear box  17  of a motor vehicle, represented on  FIG. 10 . The power take-off cooperates with an output shaft of gear box  17 . Obviously, casing  3  comprises means for attaching on the gear box  17  of the motor vehicle. 
         [0030]    In an advantageous embodiment, the power take-off  2  is provided with a device for limiting the transmitted torque, not shown. This device makes it possible to protect the transmission members in the case where a mobile shaft of device  1  is blocked. 
         [0031]    In a first embodiment of the invention, the power take-off  2  comprises, at the output side, a pinion  4 , illustrated on  FIGS. 1  a and  2 , and constituting a multiplication stage. The pressurizing device comprises a frame  5  to be associated with casing  3  of power take-off  2 . In addition, the pressurizing device  1  comprises, in the represented embodiment, two rotatably movable shafts  6   a,    6   b  on frame  5 , respectively around parallel first A and second B axis. Each one of shafts  6   a,    6   b  bears a compression screw, not shown, extending in a compression room of the device  1 . Device  1  comprises fluid supply and fluid output openings communicating with the compression room. 
         [0032]    Both screws have complementary profiles and fit into each other, however, without being in contact with each other. A female screw has concave shaped lobes and the other, male, screw has convex shaped lobes. During operation, in order to compress the fluid, the first screw rotates in a first rotation direction whereas the second screw rotates in a second rotation direction. In a particular embodiment of the invention, the female screw has 6 concave shaped lobes whereas the male screw has 5 convex shaped lobes. Owing of the number of different lobes, relative speeds are in a ratio of 5/6 or 6/5 depending on the screw taken in reference. 
         [0033]    The rotations of the screws are synchronized. To this end, shafts  6   a,    6   b  each bear a gear wheel  11   a,    11   b  cooperating together. Both gear wheels  11   a,    11   b  form means for the synchronization of the rotation of shafts  6   a,    6   b  making it possible to drive said shafts in reversed rotation directions. Of course, the synchronization means will be adapted so as to respect the rotation speed ratios between the screws. It is to be noted that any equivalent means for fulfilling the function of synchronizing the rotation speeds may be used. 
         [0034]    In addition, one of the shafts  11   a,    11   b  supports a coupling means forming pinion  7  forming a coupling means with the output pinion  4  of the power take-off  2 . Coupling means forming pinion  7  has a size and a number of teeth lower than the size and the number of teeth of the output pinion  4  of the power take-off  2  so as to secure a multiplication of the rotation speed. Herein, for example, the multiplication ratio is about 3. Thus, during operation, the movable shafts  6   a,    6   b  may be driven at high rotation speeds of about 10000 to 20000 rotation/minute for example. 
         [0035]    Advantageously, pinion  7  is removable and may, alternatively, be mounted on an end of the first shaft  6   a  or the second shaft  6   b.  This embodiment makes it possible to adapt the pressurizing device  1  to the various gear boxes available on the market. Indeed, the output shafts of gear boxes  17  available on the market can indifferently be rotationally driven in a clockwise or anti-clockwise direction. Also, by positioning the pinion  7  on either one of the shafts, the pressurizing device  1  adapts to the various types of existing gear boxes  17  and power take-offs. 
         [0036]    Consequently, before mounting the device on a power take-off, pinion  7  will be positioned on the first  6   a  or the second shaft  6   b,  depending on the rotation direction of the power take-off  2 . Thus, whatever the direction of rotation of the power take-off  2 , the first shaft  6   a  can always be driven in the first rotation direction and the second shaft  6   b  be driven in the second rotation direction. 
         [0037]    It will be noted that the axes of both shafts  6   a,    6   b  are disposed at an equal distance from the axis of rotation C of the output pinion  4 , for permitting the driving of either one of both shafts. Moreover, in order to allow the assembly of pinion  7  on either one of shafts  6   a,    6   b,  shafts  6   a,    6   b  comprise ends for receiving pinion  7 , identical and adapted to receive the central bore of pinion  7 . In order to secure pinion  7  to shafts  6   a,    6   b,  it will be noted that the central bore of pinion  7  comprises longitudinal splines  15  engaging with longitudinal grooves  16  of shafts  6   a,    6   b.    
         [0038]    In addition, it is noted that shaft  6   a,    6   b  which does not support pinion  7  supports a removable protection spacer  14 . Of course, to allow for the interchangeability of pinion  7  and spacer  14 , the bores of pinion  7  and spacer  14  are identical. Thus, the adaptation of the device depending on the rotation direction of the power take-off is carried out by permuting the position of spacer  14  and pinion  7  on both shafts  6   a,    6   b.  The spacer  14  has obviously an external diameter lower than the diameter of pinion  7 , so that, when the device is associated with the power take-off, the spacer  14  do not contact output pinion  4  of the power take-off  2 . 
         [0039]    In addition, it is to be noted that, owing to the design, the rotation speeds on the outlet side of gear boxes  17  are different. Moreover, this difference in speed usually depends on the rotation direction, be it clockwise or anti-clockwise, at the output side of gear box  17 . Consequently, to allow an optimal operation of the device whatever the type of gear box  17  used, it can be provided that the rotation speeds of each screw be identical, during operation and that the speed ratio between the screws be substantially identical to the rotation speed ratio between the gear boxes whose output is driven in the clockwise direction and the gear boxes whose output is driven in the anti-clockwise direction. 
         [0040]    Typically, the output speed ratio between the two types of boxes is about 1.15. Thus, the gear wheels  11   a,    11   b  exhibit sizes and numbers of teeth adapted to the 6/5 ratio of the lobes of the male and female screws. This ratio of 1.2 is astutely used in relation to ratio 1.15 of the box types so as to maintain the speed of the driving engine at the most suitable load between 1200 rotations per minute and 1400 rotations per minute approximately. 
         [0041]    In addition, frame  5  comprises means for attaching to casing  3  of the power take-off  2 . These means are able to bear and support pressurizing device  1 . In other words, the pressurizing device  1  is only fixed and supported via these means and is not directly attached by other means to the vehicle body. Thus, frame  5  may be regarded as self-supporting. 
         [0042]    The support and attaching means comprise a peripheral mounting flange  8  which is adapted to cooperate with casing  3  of power take-off  2 , via an appropriate mounting flange  13  of casing  3  for example. The mounting flange  8  comprises bores to face threaded bores formed on casing  3 . The bores allow the passage of fixing members  10 , such as screws, cooperating with the threaded bores of casing  3 , so as to secure pressurizing device  1  to casing  3 . 
         [0043]    The mounting flange  8  has a particular form. In fact, the mounting flange  8  comprises a first portion running along the periphery of frame  5  and a second, substantially circular, cradle-shaped, portion, whose center corresponds to the center of rotation C of the output pinion  4  of the power take-off  2 . The second portion of the mounting flange  8  allows the passage of the output pinion  4  of the power take-off  2  so that pinion  7  directly cooperates with the output pinion  4 . 
         [0044]    In addition, the mounting flange  8  is also provided with centering and positioning means of centering and positioning with respect to casing  3 . These centering and positioning means provide a precise dynamic coupling between power take-off  2  and pressurizing device  1 . 
         [0045]    In the embodiment represented in  FIGS. 2 and 3 , the centering and positioning means comprise cavities  9  for receiving complementarily-shaped pawns, formed on casing  3 . Obviously, in an equivalent embodiment, cavities  9  could be formed in casing  3  whereas the complementarily-shaped pawns are borne by mounting flange  8 . Moreover, it will be noted that the pawns must have a sufficient length and mechanical resistance for supporting the device. 
         [0046]    Also it is to be noticed, from  FIG. 3 , that the centering and positioning means will advantageously only comprise two cavities  9  and that straight line D crossing these two cavities also passes by the center of rotation C of the output pinion  4  of power take-off  2 . Thus, the positioning of device  1  with respect to the power take-off  2  is precisely secured by limiting the number of cavities  9  used. In addition, the positioning pawns could be of cylindrical form, conical form or more generally of any suitable form. 
         [0047]    In another embodiment, represented on  FIG. 4 , the mounting flange  8  comprises a structure of female, or male, fitting structure  18 , for receiving a mating fitting structure formed on the mounting flange  13  of the casing of the power take-off  2 . In addition, in some cases, the rotary members of the compressor may require a forced lubrication. Thus, in an advantageous embodiment, the pressurizing device  1  comprises an internal lubricating circuit and means for the connection of the internal circuit to a lubricating circuit of the motor vehicle. In this case, the internal circuit of device  1  is connected to a lubricating circuit of the vehicle, located in the power take-off for example, and comprising a tank and a pump to provide for the flow of lubricant towards the internal circuit of device  1 . 
         [0048]      FIGS. 5 to 8  illustrate in a detailed manner the internal lubricating circuit. Herein, the lubricating circuit of the motor vehicle is conveyed to the device via the support shaft of the output pinion  4 , not represented, whose internal bore forms a lubricant conveying conduit. The end of the support shaft of the output pinion  4  is introduced into a supply opening  19  of the device extending along axis of rotation C of the output pinion  4 . To secure a precise positioning of the supply opening  19  with respect to the support shaft output pinion  4 , the positioning pawns formed on casing  3 , have a sufficient length to allow for the positioning of device  1  with respect to the power take-off  2  before the introduction of the shaft end into the supply opening  19 . 
         [0049]    The lubricant is then conveyed from supply opening  19  to a lubricant filter  21  by means of a first channel  20 , represented on  FIG. 6 . At the output side of filter  21 , purified lubricate is then conveyed to bearings  22   a,    22   b  of shafts  6   a,    6   b  via a second conduit  23 , represented on  FIGS. 7 and 8 . The bearing support cores  23   a,    23   b,  have lubricant passage slits  24   a,    24   b.  Thus, lubricant flows downward by gravity towards the bottom of frame  5 . Thereafter, the lubricant could be collected by means of a pumping device borne, for example, by the power take-off. 
         [0050]    Advantageously, the fluid pressurizing device  1  has a mass and dimensions arranged such that the loads applied by the device, associated to the power take-off, are lower than the permissible loads at the junction of the power take-off on the gear box. To this end, the dimensions as well as the thickness of the frame walls are optimized. Besides, in order to decrease the volume of the compression room and thus of the frame  5 , it is intended that compression screws will be driven at high rotation speeds. To this end, the coupling pinion  7  and/or the output pinion  4  of the power take-off  2  are adapted to drive the movable shafts at speeds of about 10000 to 20000 rotations per minute. 
         [0051]      FIGS. 10 and 11  illustrate a second embodiment of the invention. As in the preceding embodiment, device  1  comprises a frame  5 , supporting two movable shafts  6   a,    6   b  rotatable in opposed rotation directions, synchronization means and a removable pinion  7  to be alternatively assembled on the first  6   a  or the second shaft  6   b  depending on the rotation direction of said power take-off  2 . However, in this embodiment, unlike the first aspect of the invention, device  1  comprises a device for multiplying the rotation speed, composed of a succession of gears  26 ,  27 ,  28  whose sizes are adapted to obtain the desired multiplication ratio. 
         [0052]    In addition, the device comprises a splinned shaft  25 , illustrated on  FIG. 10 , to be engaged in a rotary sleeve of the power take-off. Moreover, the device comprises a mounting flange  26  to be mounted on casing  3  of the power take-off  2 . This device  1  may be adapted to the various gear boxes and power take-offs available on the market. It will be noted however that the encumbrance and weight of the device obtained according to the second embodiment are higher than those of the device obtainable in accordance with the first embodiment. Nevertheless, this embodiment could be appropriate in the case of solutions requiring low compression power, whose weight and size remain moderate. 
         [0053]    The invention is described above by way of example. It is to be understood that a man skilled in the art is capable of performing various alternative embodiments of the invention without departing from the scope of the invention.