Switching device for reciprocating pumps

Abstract: A reciprocation switching device for a pump, said device including a switching device body (111); a switching valve chest (122) provided inside said switching device body; a working rod (113) inserted through said switching valve chest and reciprocated by working fluid alternately supplied into and discharged from two working fluid chambers (118,119); a switching operator (123) fitted around said working rod so as to be able to slide in the axial direction of the rod and to be moved to one side or the other side of said switching valve chest; a cavity-shaped switch (127) activated by said switching operator so as to switch supply and discharge of working fluid, which has been supplied into said switching valve chest, into and from said two working fluid chambers; and spring means to hold said switching operator at one side or the other side of the switching valve chest by applying to it spring pressure in a direction perpendicular to said switching operator when said switching operator is at a neutral point whereat no displacement force is impressed thereon by said spring means; said spring means comprising at least one wire spring (164) made into a C-shape by bending both ends of wire material with a circular cross section so that the ends face each other; said at least one wire spring having a straight portion (171) between both ends (172) thereof, said both ends being straight and colinear, said straight portion and said both ends being parallel to each other, both ends of said at least one wire spring being fitted into holes (174) horizontally bored in said switching operator; and said straight portion of said at least one wire spring being fitted in a spring holder (163) provided so as to face said switching valve chest so that said straight portion is able to rotate therein.

Description: The present invention relates to a switching device for pumps reciprocated by automatically switching application and removal of fluid pressure. Conventional reciprocation switching devices for pumps typically comprise, as described in Japanese Utility Model Publication No. 40805/1974, a piston fitted to the inside of a cylinder body to slide therein; the said piston having two kinds of movable valves to control fluid pressure applied to one side of the piston and fluid pressure applied to the other side of the piston; a valve operator installed at the centre of the piston to operate the two valves by snap-action by means of a spring working in relation to the reciprocating movement of the piston. As a compressed coil spring is used for such a conventional device, it requires a spring fitting rod for attaching the spring; a structure that permits this rod to be fitted to rotate around the valve operator installed at the centre of the device; and a spring holder section fitted to the said spring fitting rod to slide against it and also to rotate around sections incorporated with the piston as one body. Therefore, such a conventional device presents a problem in that assembly of those parts as described above is difficult and complicated and cost reductions are limited due to the numerous parts required. A known example of a conventional reciprocation switching device for a diaphragm pump is described in Japanese Patent Publication No. 40805-1974. A device described therein consists of, as shown in Fig. 16, switching mechanism section 512 provided inside switching device body 511; working rod 515 inserted through said switching mechanism section 512 and reciprocated by working fluid supplied to and exhausted from two working fluid chambers 513 and 514 in turn; switching operator 519 fitted between the larger diameter section 516 of said working rod 515 and sleeve 517 capable of moving and being moved to one side or another of switching valve chest 518; cavity-shaped switch 521 switched by said switching operator 519 to switch supply and exhaust to and from two working fluid chambers 513 and 514 of working fluid supplied to switching valve chest 518; and spring 522 to hold switching operator 519 at one side or the other of switching valve chest 518 by applying spring pressure perpendicular at the neutral point to said switching operator 519. Such conventional devices operate by moving switching operator 519 by reciprocating movements of working rod 515; sliding switch 521 by said switching operator 519; controlling supply and exhaust of working fluid (the air) from and to the two working fluid chambers (air chambers) 513 and 514; and continuously reciprocating working rod 515. Diaphragms 523 and 524 are a part of both ends of said working rod 515. These diaphragms 523 and 524 partition the chambers to form said working fluid chambers 513 and 514 and pump chambers 525 and 526. As said working rod 515 moves, volumes of said pump chambers 525 and 526 change, thus creating pumping strokes. For example, when working rod 515 moves towards the right, the liquid contained in chamber 525 at one side of the device is forced, by volumetric reduction of said pump chamber 525, out of discharge port 528 through check valve 527 at the discharging side. Meanwhile, the liquid is sucked, by volumetric expansion of pump chamber 526 at the other side, out of suction port 529 into said pump chamber 526 through check valve 530 provided at the suction side. Such right and left pumping action is repeated in turn by the automatic switching of working fluid at said switching mechanism section 512. In such conventional reciprocation switching devices, the configuration for the spring exerting pressure to switching operator 519 involves attaching cylindrical slider 531 to one end of compressed coil spring 522; insetting one ball-shaped end 534 of activator 533 in cavity 532 at the end of said slider 531, to allow the ball-shaped end 534 to rotate; and insetting the other ball-shaped end 535 of activator 533 in a cavity 536 of said switching operator 519 to permit rotation thereof. Thus, compressed coil spring 522 is used in a conventional structure, and therefore it is necessary to install said cylindrical slider 531 and activator 533 between said spring 522 and switching operator 519, a configuration which presents difficulty. Such a conventional configuration further presents a problem in that, as cavity-shaped switch 521 slides along the working rod, abrasion tends to occur between said switch 521 and the opposing metal and it thus becomes necessary to use special wear-resistant metal at such sliding section. From US-A-3 699 846 (D1) there is known a reciprocation switching device for a pump, according to the pre-characterising clause of claim 1. The objective of the present invention is, by using a spring of a special shape for the snap action of the reciprocation switching device for a pump, to permit installation of such spring directly in the valve operator or the switching operator so that number of parts can be reduced, to facilitate assembly; and to reduce cost of the device compared to conventional devices. Another objective of the present invention is to improve durability of the valve configuration without using special metals. A further objective of the present invention is to make it considerably easier to attach the spring used for the snap action of a reciprocation switching device for a pump. A further objective of the present invention is to make the diameter of such reciprocation switch device smaller. It is possible to considerably reduce the number of parts compared with a conventional device using pressure coil springs and to make installation of such wire spring much easier. Thus product cost can be significantly reduced. The present invention provides a pump including a reciprocation switching device therefor, said device including a switching device body (111); a switching valve chest (122) provided inside said switching device body; a working rod (113) inserted through said switching valve chest and reciprocated by working fluid alternately supplied into and discharged from two working fluid chambers (118,119); a switching operator (123) fitted around said working rod so as to be able to slide in the axial direction of the rod and to be moved to one side or the other side of said switching valve chest; a switch (127) defining a cavity (128) activated by said switching operator so as to switch supply and discharge of working fluid, which has been supplied into said switching valve chest, into and from said two working fluid chambers; and spring means to hold said switching operator at one side or the other side of the switching valve chest by applying to it spring pressure in a direction perpendicular to the sliding direction of said switching operator when said switching operator is at a neutral point whereat no displacement force is impressed thereon by said spring means; characterised in that said spring means comprises at least one wire spring (164) made into a C-shape by bending both ends of wire material with a circular cross section so that the ends face each other; said at least one wire spring having a straight portion (171) between both ends (172) thereof, said both ends being straight and colinear, said straight portion and said both ends being parallel to each other, both ends of said at least one wire spring being fitted into holes (174) horizontally bored in said switching operator; and said straight portion of said at least one wire spring being fitted in a spring holder (163) provided so as to face said switching valve chest so that said straight portion is able to rotate therein. According to the present invention, as working rod 113 moves, switching operator 123 is also moved; as said switching operator 123 approaches the neutral point, wire spring 164 between switching operator 123 and spring holder 163 rotates with its straight portion 171 as the fulcrum and is simultaneously compressed; the switching operator having passed the neutral point, restoring force conserved in wire spring 164 is immediately released in the direction where the working rod is moving to; and switching operator 123 fitted around working rod 113 to be movable along it is instantly moved, as far as its fitting allows, to its terminal point in the moving direction of the rod. At this moment, switching operator 123 is caught by switch 127, which is also moved immediately; and supply and discharge of working fluid from and into working fluid chambers 118 and 119 is switched instantly. Assembling of the parts calls for inserting both ends of wire spring 164 into switching operator 123 and fitting spring holder 163 to the straight portion 171 of said wire spring 164. Pressure is applied from said spring holder 163 to wire spring 164. According to the present invention, installation of the spring in the switching valve chest is facilitated, requiring only fitting the wire spring to the switching operator and setting the spring holder, and the number of required parts can be reduced. Therefore, product cost can be reduced compared to conventional devices. The present invention has a benefit in that the number of parts required can be reduced and that installation of the spring is much easier, so that a large scale reduction in cost is possible. Furthermore, because supply and discharge of working fluid is switched by means of contact with and separation of valves from valve seats, no part of the valve structure is exposed to abrasion, so that deterioration of durability due to abrasion can be prevented. The present invention has the benefit in that the number of parts required can be considerably reduced from that required for a conventional device using a compressed coil spring and that installation of the spring is facilitated, so that a large scale reduction of product cost is possible. Furthermore, because valve seats and valves are installed by means of the valve seat attaching section at the upper part of the cylinder body, it is possible to make the diameter of the piston and the cylinder smaller. The present invention has the benefit in that passage for supply of working fluid can be compactly provided in the centre of the valve body and the diameter of reciprocation switching device of this kind can be smaller. In order that the invention may be readily carried into effect, embodiments thereof will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a schematic sectional view of a reciprocation switching device according to an embodiment of the present invention, Figure 2 is a schematic horizontal sectional view of a principal part of Figure 1; and Figure 3 is a schematic sectional view of a diaphragm pump equipped with a conventional reciprocation switching device. Description of Embodiment As shown in Fig. 1, cylinder 112 is screwed air-tight over the left end of switching device body 111; working rod 113 is inserted into the centre of switching device body 111 capable of movement; washer 114 and cap nut 115 are screwed over the left end of said working rod 113; piston 117 comprising a pair of discs 116 and packing is sandwiched and thus supported by said washer and nut. Left working fluid chamber 118 and right working fluid chamber 119 are provided inside cylinder 112 with said piston 117 in between. Intake port 121 to which the compressed air is to be supplied is provided on the switching device body 111 side and leads to switching valve chest 122 formed at the centre of switching device body 111. Inside this switching valve chest 122, switching operator 123 is fitted around said working rod 113 capable of sliding along it within the specified scope. A cavity is formed at the top of switching operator 123; and at both ends of said cavity, catching ridges 124 are formed perpendicular to the moving direction of the operator. Guide plate 125 is attached to the device body 111 to face the upper surface of said switching operator 123, and switch 127 is fitted to said guide plate 125 capable of movement in the direction of the rod. Said switch 127 has a cavity 128 at its upper end. Metal plate 131 with high abrasion resistance is fitted to the surfaces which slide against said switch 127, switch 127 having the same high abrasion resistancy, and air supply vent 132, exhaust vent 133 and air supply vent 134 are bored in said metal plate 131. Each of these vents 132, 133 and 134 are respectively connected to air supply vent 135, exhaust vent 136 and air supply vent 137 bored in switching device body 111; and air supply vent 137 further leads to connecting port 138 bored in body 111. Pipe 143 is connected, through elbow 141 and pipe joint 142, to said connecting port 138, which is further connected to connecting port 146 of cylinder 112 through pipe joint 144 and elbow 145. Said working rod 113 is provided with bush 151 fitted to the left side of switching operator 123 and the large diameter section 152 at the right. Housing 154 is fitted to bush 151 through O ring 153, and packing 155 is fitted to the large diameter section 152. At the bottom of said switching valve chest 122, tapped hole 161 with a large diameter is provided, together with plug 162 screwed into it. Disc-shaped spring holder 163 is fitted to the top of plug 162 to rotate freely; and wire spring 164 formed with wire material of round section (e.g. piano wire) is provided between said spring holder 163 and switching operator 123. Tool catching holes 165 are bored in the outer surface of plug 162 to rotate this plug 162, to the outer surface of which O ring 166 is fitted to maintain airtightness of switching valve chest 122. As shown in Fig. 2, wire spring 164 is formed into a C-like shape with straight portion 171 at its centre and both ends 172 bent to face each other. Straight portion 171 of said wire spring is inset in groove 173 of spring holder 163 so that the spring is able to rotate by virtue of its circular cross section. Further, both ends 172 of wire spring 164 are so fitted into holes 174 horizontally bored in the centre of said switching operator 123 as to be able to rotate. Ridge 175 to set its position in relation to plug 162 is formed at the bottom of spring holder 163. Procedures for fitting said wire spring 164 require inserting wire spring 164 into switching valve chest 122 through tapped hole 161, from which plug 162 has been previously removed; inserting the ends 172 of the spring, while applying force to enlarge the space between the ends, into holes 174 at both sides of switching operator 123; and screwing plug 162, to which spring holder 163 has already been fitted, capable of rotation, to said tapped hole 161. Whilst screwing in the plug 162, although spring holder 163 initially rotates with plug 162, groove 173 of spring holder 163 becomes locked with straight portion 171 of wire spring 164 as plug 162 proceeds, spring holder 163 ceases to rotate and only plug 162 is rotated. Pump casing 181 is incorporated to the right side of body of switching device 111; working rod 113 is incorporated with piston rod 184 through connecting section 183 screwed over threaded portion 182 at the right end of working rod 113; piston 186 is incorporated at the end of said piston rod 184 through connecting section 185; ball 192 is provided inside suction port 191 open at the end of said casing 181 for checking counterflow; ball 194 is provided inside through-hole 193 open at the centre of said piston 186 for checking counterflow; through-hole 195 is provided at said connecting section 185; and said through-hole 195 is connected, via inside pump casing 181, to pump casing screw socket 196 provided in switching device body 111, which socket 196 further leads to discharge port 198 via through-hole 197. In Fig. 1, a reciprocating pump is shown sideways but in use the device is used in the vertical, standing position. Action of a device according to the present embodiment will be described hereunder; The air supplied under pressure from air intake port 121 into switching valve chest 122 is supplied through air supply vents 134 and 137, connecting port 138, pipe 143, etc. into working fluid chamber 118, internal pressure of which moves piston 117 to the right, and thus the air inside working fluid chamber 119 is expelled through air supply vent 135, cavity 128 of switch 127 and exhaust vents 133 and 136. This rightward movement of piston 117 results in, via working rod 113, movement of pump piston 186 to the right, and the liquid at the right side of piston 186 is transported to the left side of pump casing 181 through through-holes 193 and 195. Near the end of this movement of working rod 113 to the right, switching operator 123 is moved to the right by bush 151; wire spring 164 is rotated to the right with its straight portion 171 as the fulcrum; as far as the neutral point shown in Fig. 3 both ends 172 of wire spring 164 are applied with compressive pressure in the direction that they approach straight portion 171 so that spring force is conserved in wire spring 164; when the wire spring has passed the neutral point shown in Fig. 3 by even a short distance, repelling force conserved in wire spring 164 is instantaneously released to the right; and wire spring 164 rotates instantly from the said neutral point to the right and simultaneously pushes switching operator 123 to the right of switching valve chest 122. With this instantaneous movement of switching operator 123 switch 127 is also transported to the right instantly; exhaust vent 133 and air supply vent 134 become connected with cavity 128; and switching valve chest 122, where pressurized air is supplied, becomes connected to air supply vent 132. As a result compressed air is supplied from switching valve chest to working fluid chamber 119 through air supply vent 135; piston 117 is moved to the left, the air pushed out of working fluid chamber 118 is discharged out of the device through pipe 143, air supply vents 137 and 134, cavity 128 which has been moved, and exhaust vents 133 and 136. This leftward movement of piston 117 is conveyed, through working rod 113, to pump piston 186, with the leftward movement by which the liquid at the left of said piston 117 is discharged out of the pump through hole 196 and through-hole 197, and simultaneously liquid is sucked from suction hole 191 into pump casing 181. Near the limit of this leftward movement of working rod 113, large diameter section 152 locks with switching operator 123, which moves to the left together with working rod 113; with this movement wire spring 164 is rotated in the left direction indicated in Fig. 3 with its straight portion 171 as the fulcrum; as described hereinabove, spring force is conserved in wire spring 164 as far as the neutral point and having passed this point, repelling force conserved in wire spring 164 is instantaneously released so that switching operator 123 is switched to the left instantly as well as switch 127. Such actions as described above are repeated so that reciprocating action to drive the pump is continued. Although, according to the embodiment shown in the drawings, plug 162 is screwed in order to attach spring holder 163 for wire spring 164, said plug 162 is not always necessary: for instance, the spring holder may alternatively be fitted airtightly to the hole in switching device body 111, the flange provided at said spring holder being bolted to the body 111.

Claims: A pump including a reciprocation switching device therefor, said device including a switching device body (111); a switching valve chest (122) provided inside said switching device body; a working rod (113) inserted through said switching valve chest and reciprocated by working fluid alternately supplied into and discharged from two working fluid chambers (118,119); a switching operator (123) fitted around said working rod so as to be able to slide in the axial direction of the rod and to be moved to one side or the other side of said switching valve chest; a switch (127) defining a cavity (128) activated by said switching operator so as to switch supply and discharge of working fluid, which has been supplied into said switching valve chest, into and from said two working fluid chambers; and spring means to hold said switching operator at one side or the other side of the switching valve chest by applying to it spring pressure in a direction perpendicular to the sliding direction of said switching operator when said switching operator is at a neutral point whereat no displacement force is impressed thereon by said spring means; characterised in that said spring means comprises at least one wire spring (164) made into a C-shape by bending both ends of wire material with a circular cross section so that the ends face each other; said at least one wire spring having a straight portion (171) between both ends (172) thereof, said both ends being straight and colinear, said straight portion and said both ends being parallel to each other, both ends of said at least one wire spring being fitted into holes (174) horizontally bored in said switching operator; and said straight portion of said at least one wire spring being fitted in a spring holder (163) provided so as to face said switching valve chest so that said straight portion is able to rotate therein. A reciprocation pump including a switching device as claimed in claim 1, wherein said spring means consists of said at least one wire spring (164), said at least one wire spring (164) providing the sole spring force acting on said switching operator (123).

Inventors: MURATA MINORU, YAMADA KAZUMASA, MURATA, MINORU, YAMADA, KAZUMASA
Applicants: YAMADA YUKI SEIZO CO LTD, YAMADA YUKI SEIZO CO. LTD.
Application year: 1988
Main classification: F01L21
IPC codes: F01L23, F01L31, F01L21, F04B9, F04B43