Abstract:
A hand-operated inflator with dual cylinder is provided. Once the cylinders are pulled out on two sides of the central block to form a line axially, and a clamp plate at mid point in between the two cylinders is turned to the transversal position to lock the cylinders in place, the inflator is set for refilling operation. The two cylinders can be folded back when the clamp plate is released, making it easy for carrying and storage with the length reduced by half. The inflator is able to inflate an object with faster rate as compared with the conventional inflators with only one air cylinder. Moreover, the central block can be attached with a pressure meter. If the measured air pressure inside the object gets excessively high, air can be safely released through an over pressure valve.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a hand-operated inflator, and in particular to an inflator having dual cylinder design, so that an object can be inflated at a faster rate using less effort. 
   2. The Related Art 
   Generally, an air pump or hand-operated inflator is used to inflate tires, balloons, inflatable toys or other inflatable objects. Commonly seen hand-operated inflators have one air cylinder. The refilling of an inflatable object may take a long time and is not an easy task for ordinary users. 
   A recent design of the inflator employs two air cylinders, which is comprised of a base block and two cylinders coupled on two sides of the base block. The dual-cylinder inflator is attached with a discharge tube that has a mouthpiece on the other end for fitting on to the air nozzle of an inflatable object. 
   The dual-cylinder design is intended to expedite the refilling operation. The inflator uses the two pistons in the two air cylinders to compress the internal air at the same time, so that twice the amount of compressed air is generated in one stroke, as with the conventional one-cylinder inflator. The object can thus be fully inflated much faster than using the one-cylinder inflator. 
   However, the dual-cylinder inflator which boosts faster refilling might not be that attractive for ordinary users, as the dual-cylinder inflator is usually larger and weighs more than the one-cylinder inflator. 
   The air cylinders and the base block have to be assembled by thread mounting the air cylinders onto the base block. When the refilling is done, the dual-cylinder inflator is usually taken apart to save storage space. The assembling and disassembling of the dual-cylinder inflator may be quite troublesome, and, even when disassembled, all parts have to be kept in good order in order to use them again for the next time. 
   To overcome the above-mentioned problems, the present invention intends to provide an improved dual-cylinder inflator that is easy to use and small enough to be stored away conveniently. 
   SUMMARY OF THE INVENTION 
   The primary objective of the present invention is to provide an inflator with two foldable air cylinders, making it easy to use and maintain at the same time. Such inflator has two symmetrical cylinders on two sides, which are pivotally mounted on the central block, whereby the inflator can be completely set up simply by pulling out the two cylinders along respective pivot joints, with the two cylinders aligned on opposite sides of the central block to form a line axially. 
   With regard to the manner of operation, the user is to steadily push in the handles of the inflator with both hands, and the pistons compress the air in the dual cylinder and force the compressed air through the outlet of the central block into the inflatable object, so the object can be fully inflated with a faster than that using the single-cylinder inflator. 
   One of the main features of the present design is that the hand inflator employs two pivot joints to connect with the two cylinders. When in the expanded form, the two cylinders are rotated by 90 degrees in the expanding manner to form a line axially, whereas in the knocked down form, the cylinders are rotated by 90 degrees in the folding manner to save space. 
   When the inflator is set up, that is the cylinders and the central block are aligned to form a line axially, an internal air path from the cylinders to the central outlet is created passing through the interior of the central block, pivot pins, and cylinders. 
   The present invention is characterized in that the central block is attached with a pressure meter so that the air pressure in the object can be precisely monitored to get an appropriate pressure level. The hole on one side of the central block used to hold the pressure meter leads to internal space that communicates with longitudinal conduits in the pivot pins. 
   The present invention is also characterized in that the hand inflator is also be equipped with an over pressure valve. If the measured air pressure inside the object gets excessively high or reaches over a preset limit, air can be safely released through the over pressure valve. 
   The present invention is also characterized in that a clamp plate is used to hold the two cylinders in place after the cylinders are aligned on opposite ends of the central block. 
   In accordance with the present invention, to set up the inflator for refilling operation, the two symmetrical cylinders are rotated by 90 degrees in expanding manner, so that the two cylinders are aligned on opposite sides of the central block to form a line axially. The clamp plate is then rotated to the transversal position to lock the two cylinders in place in order to prevent waggling of the cylinders during the refilling operation. 
   To fold down the inflator, the clamp plate is rotated to the longitudinal position to allow the inflator to be folded down by rotating each cylinder 90 degrees in folding manner to form right angle with the central block. The length of the inflator in the knocked down form is almost half of the fully expanded form, thus making it easy to carry and to store away the inflator when not in use. 
   The present invention will become more obvious from the following description when taken in connection with the accompanying drawings, which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of an inflator in accordance with the present invention; 
       FIG. 2  is an exploded view of the inflator assembly; 
       FIG. 3  is a sectional view showing internal structure of the main parts of the inflator; 
       FIG. 4  is a sectional view of part of the cylinder; 
       FIG. 5  is a sectional view of an over pressure valve; 
       FIG. 6  is a diagram of the inflator with a clamp plate in longitudinal position (unlocked); 
       FIG. 7  is a diagram of the inflator in knocked down form when not in use; and 
       FIG. 8  is a sectional view of the clamp plate and the cylinders in locked position. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A hand-operated inflator constructed in accordance with an preferred embodiment of the present invention as shown in  FIGS. 1 and 2 , comprises a central block  1 , two pivot pins  2 , and two cylinders  3  each having a free end forming a handle  31 . The central block  1  has a discharge tube  5  attached to a central outlet  13  on the back surface, an pressure meter  4  mounted at the center point on the front surface, an over pressure value  7  received on one side, and two slots  11  formed on the lower portion of each side. The two cylinders  3  each having a protruded portion on one end are fitted into the slots  11  and rotatably connected by pivot pins  2 . 
   In the air refilling process, the user can monitor the actual pressure inside the object through the pressure meter  4  as the object is being refilled. If the pressure inside the object gets excessively high, air pressure can be released by the over pressure valve  4  until the preset pressure is reached. 
   The inflator also has a hole  12  on the lower portion of the back surface of the central block  1 , as shown in  FIG. 8 , at the mid point between the two cylinders  3 , in which a screw  61  is inserted through a spring  62  to secure the clamp plate  6  with proper damping. 
   Referring to  FIGS. 2 and 3 , there are two through holes  15  beginning from the top surface to the bottom surface that pass through the internal space and the slot cavity  11  of the central block  1 , respectively corresponding to the two pivot pins  2  which are inserted from the bottom holes  15  into the central block  1 . Two screws  27  with gaskets are respectively inserted into the top holes  15  to secure one end of the pivot pins  2  inserted through the bottom holes  15 . 
   The through hole  14  on one side of the central block  1  used to receive an over pressure valve  7  is to communicate with the two through holes  15  at the internal intersection points. 
   The hole (not shown) on the front surface of the central block  1 , opposite to the central outlet  13  on the back surface, is used for mounting the pressure meter  4 . 
   Referring to  FIG. 8 , the clamp plate  6  is rotatably mounted by a screw  61  on the back side surface of the central block  1 , so that the clamping plate  6  can be rotated to the transversal position to fit into the indent  39  on the outer rim of each cylinders  3  after the cylinders  3  are expanded to form a line axially, so that the clamp plate  6  can be rotated to the transversal position to hold down the two cylinders  3  to prevent any waggling of the cylinders  3  during the refilling operation. If the clamp plate  6  is rotated to the longitudinal position, the cylinders  3  can be folded down to form a right angle with the central block  1 , thus the length of the extended inflator is almost reduced by half. 
   Each one of the two pivot pins  2  is built in with a longitudinal conduit  21  passing through the hollow core in the extension portion. Each pivot pin  2  has a first circular band recess  24  around the neck of the conduit  21 , and a second circular band recess  25  near the open end, wherein the first circular band recess  24  has a hole  22  on the bottom surface, and the second circular band recess  25  also has a hole  23  on the bottom surface, whereby the holes  22 ,  23  communicate with each other through the longitudinal conduit  21  running through the axis of the pivot pin  2 . The circular band recesses  24 / 25  are each blocked by a pair of O-rings  26  to prevent air leakage in the gap between the pivot pin  2  and the through hole  15 , and the free end of the longitudinal conduit  21  in each of the two pivot pins  2  is sealed off by a screw  27 , which is used to secure the cylinder  3  in place. 
   Referring to  FIG. 4 , each cylinder  3  comprises a cylindrical body  32 , a central shaft  311  connected by a piston  312  on one end and a handle  31  on the other end, and a header  33 . One end of the cylindrical body  32  is to receive a valve block  34 , wherein a spring  36  is placed between a movable plug  37  and a circular pad  35  to form a check valve in order to prevent air flow in the reverse direction. 
   When the two cylinders  3  and the clamp plate  6  are aligned on the opposite side of the central block in a line axially, the position of the first circular band recess  24  corresponds to the central conduit of the 331 of the header  22  of the cylinder  3 , and the second circular band recess  25  corresponds to the transversal through hole  14  of the central block, thereby the longitudinal conduits  21  in the pivot pin  2  communicate with the transversal through hole  14  extending from the lateral wall of the central block  1  to reach the second longitudinal through hole  15 , and the longitudinal conduits  21  in the pivot pins  2  communicate with the central conduits  331  of the cylinders  3  on two sides, so that an internal air passage is created in the inflator bridging by the longitudinal conduits  21 . 
   The cylindrical body  32  has threads on one end of the external surface, and the header  33  has corresponding threads on the inner wall of the cup-shaped portion, so that the header  33  can be coupled onto one end of the cylindrical body  32  that holds the check valve  34 . 
   The other end of the header  33  is provided with a protruded portion for fitting into the slot  11  of the central block  1 . The protruded portion has a through hole  38  from the top surface to the bottom surface for pivotally connecting the cylinder  3 . The protruded portion of the cylinder  3  also has an indent  39  on the outer rim to accommodate the rotatable clamp plate  6 . 
   The protruded portion of the header  33  is fitted into one of the two slots  11  of the central block  1 , and rotatably joined by the pivot pin  2 , so that one end of the cylinder  3  is pivotally connected with the central block  3  on each side. 
   There is a hole  351  in the center of the circular pad  35  that allows the inner space of the valve block  34  to communicate with the through hole  351 , and further through another hole  331  in the header  33 , the inner space of the valve block  34  is able to communicate with the second circular band recess. When the movable plug  37  is pushed out by the compressed air, the central conduit  332  in the cylindrical body  32  is able to communicate with the inner space of the valve block  34 . In such manner, compressed air flows from the two cylinders  3  to the central outlet  13  by way of the central conduit  332 , through hole  351 , through hole  331 , first circular band recess  24 , hole  22 , longitudinal conduit  21 , hole  23 , second circular band recess  25 , and transversal through hole  14  in that sequential order. 
   To assemble the cylinder  3  in accordance with one preferred embodiment of the invention, the protruded portion of the header  33  is first inserted into the slot  11 , with the through hole  38  aligned with the longitudinal through hole  15 , and then the pivot pin  2  is inserted from the bottom of the central block  1 , passing through the through hole  38 , with the extension portion completely covered by the central block  1 , and then the screw  27  is inserted from top hole  15  to secure the open end of the pivot pin  2 . 
   Referring to  FIG. 5 , the over pressure valve  7  comprises a metal body  71 , one side of which is cup shaped with hollow interior to receive a spring  73  and an actuating shaft  74  that has first and second relief holes  741  internally interconnected. One end of the actuating shaft  74  abuts on a button  72 , and the other end of the shaft  74  is attached with a plug  721 , which is placed over the spring  73 . In the normal conditions, the shaft  74  under the mechanical force of the spring  73  thrusts outward to seal off the first relief hole  741  on the actuating shaft  74  of the metal body  71 , and the second relief hole  741  is exposed outside the metal body  71 . When the button  72  is depressed, the plug  721  is pushed inward against the spring  73 , so that the first relief valve  741  is pushed into the metal body  71 , to allow the compressed air to be channeled through the two relief valves  741  of the shaft  74  and released to the outside. 
   To fold down the inflator, the clamp plate  6  is rotated to the longitudinal position, and the clamp plate  6  is removed from the slot  11  opening (as shown in  FIG. 6 ), so that the two cylinders  3  can be rotated by 90 degrees in the folding manner to form right angle with the central block  1  (as shown in  FIG. 7 ). The length of the inflator can be reduced almost by half. 
   To set up the inflator, the two cylinders  3  are rotated by 90 degrees in expanding manner so that the two cylinders  3  and the central block  1  of the inflator are aligned on the opposite sides of the central block  1  to form a line axially. The clamp plate  6  is then rotated to the transversal position, fitting into the indent  39  on the outer rim of the cylinder  3  to hold the cylinders  3  in place to prevent waggling of the cylinder  3  during the refilling operation. 
   With regard to the manner of operation, the user is to use the inflator by holding the right handle  31  of the inflator with the right hand, and the left handle  31  of the inflator with the left hand, and then steadily pushing in the handles  31  axially, to cause the pistons  312  to travel from one end to the other end and compress the air inside the cylindrical body  32 . 
   The compressed air respectively pushes open the plug  37  of the check valve  34  on each side of the central block  1 , the air thus enters the inner space of the check valves  34 , and further through the through hole  351  of the pad  35 , the air flows to the first circular band recess  24 , which then enters through the hole  22  into the longitudinal conduit  21  inside the pivot pin  2 , which is channeled through the hole  23  on the second circular band recess  25  to enter the transversal through hole  14 , and eventually passes through the central outlet  13  into the inflatable object. 
   When the push-in force on the handle  31  is released, the piston  312  respectively returns to the normal position, and the depressed spring  36  rebounds and pushes against the plug  37  to seal off the hole to the conduit  332  to prevent any back flow of the air stream. 
   Referring to  FIG. 5 , when the object is being inflated, the user can simultaneously monitor the pressure meter  4  as the object is being inflated. If the pressure gets excessively high, the user can depress the over pressure valve  7  to release excess air pressure until the preset air pressure is obtained. 
   When the button  72  is depressed to activate the over pressure valve  7 , the plug  721  is pushed away against the spring  73 , and at the same time, the relief hole  741  on the shaft  74  is moved into the internal space of the metal body  71 , to enable air pressure in the central block  1  to be released through the first and second relief holes  741  to the outside. 
   One of the innovative features of the present invention over the conventional designs is that the hand-operated inflator employs two pivot joints to rotatably connect one of the two air cylinders on each side of the central block. When the inflator is in the expanded form, the two cylinders are rotated by 90 degrees in the expanding manner to be aligned on opposite sides of the central block for the refilling operation, and in the knocked down form, the cylinders are rotated by 90 degrees in the folding manner to save space for storage and transport. 
   Although the present invention has been described with reference to the preferred embodiments thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.