BULK CONTAINERS & MANHOLE COVERS THEREFOR

Abstract: A pressure material container (10) in which a manhole cover (15) has a relief valve. The relief valve includes a resilient spacer ring (61) disposed between a valve seat (55) of the relief valve and a valve plate (60). A spring (50) urges the valve plate (60) of the relief valve toward the valve seat. When the fluid pressure in the container (10) exceeds a predetermined magnitude, the valve plate (60) is lifted away from the valve seat against the urgency of the spring (50) to vent the fluid in the container (10) to atmosphere. Vacuum relief apertures (75, 75′) are formed in a backing plate (66) of the relief valve. The vacuum relief apertures communicate with the fluid in the container (10) and atmosphere. A disc (70) closes the vacuum relief apertures until displaced when the fluid pressure of the fluid within the container (10) is less than atmospheric pressure to provide a path for air under atmospheric pressure to flow into the container (10) through the vacuum relief apertures (75, 75′)

Description: The present invention relates in general to a bulk material container or tank having a manhole cover, and more particularly to a bulk material container or tank having a manhole cover with a pressure-vacuum relief valve. It is desirable to provide manhole covers for bulk material containers with a pressure-vacuum relief valve. When the fluid pressure within the container or the tank is excessive, the pressure valve of the relief valve of the manhole cover opens to vent the fluid pressure of the fluid within the container or tank to atmosphere. When the fluid pressure of the fluid within the container or the tank is less than atmospheric pressure, the vacuum relief passage of the relief valve of the manhole cover provides a path for the ambient air to enter the container or tank. The application of a restraining force to secure the relief valve to the manhole cover may distort the manhole cover. The distortion of the manhole cover may influence the effectiveness of the relief valve seal or the seating of the valve plate on the valve seat of the relief valve. Thus, distortion of the manhole cover has an effect on the relieving pressure and the re-sealing pressure of the relief valve. In the employment of a plate valve for a manhole cover of a bulk material container to provide the initial pressure and vacuum relief, there is limited clearance in the opening of the plate valve because the spring constant inhibits the opening of the plate valve. Thus, the volume of the fluid passing through the opening of the plate volume may be insufficient. US-A-3,280,838 (Parkinson) describes a manhole cover for a tank which carries a pressure actuated valve unit. Low over pressures in the tank cause a valve disc to lift against gravity and open a vent path. Extreme pressure in the tank lifts the valve disc against a sealing ring and a large emergency valve then opens against the action of a spring. In the US patent to Drane, US-A-2,169,410, issued on August 15, 1939, for Breather Valve And Hatch For Tanks, there is disclosed a popoff valve plate. When the fluid pressure in the tank is sufficient to lift the valve plate against the urgency of springs, gas escapes from the tank and is vented to atmosphere. When the fluid pressure in the tank is reduced below atmospheric pressure, an inlet valve is unseated to permit air from the atmosphere to enter the tank to lessen the degree of vacuum in the tank. The US patent to Tokheim, US-A-2,152,422, issued on March 28, 1939, for Safety Device For Volatile Liquid Storage Tanks discloses a relief valve for a liquid storage tank. The relief valve is surrounded by an annular series of vacuum valves. In the US patent to Eshbaugh et al, US-A-2,164,450, issued on July 4, 1939, for Radiator Pressure cap, there is disclosed a vacuum cap valve, which unseats one spring in response to a vacuum. The surrounding enclosure of the one spring will elevate from overpressure against another spring. The US patent to Konchan, US-A-2,655,284, issued on October 13, 1953, for Radiator Pressure cap, discloses a vacuum relief valve unseating against the urgency of one spring and a pressure relief valve unseating against the urgency of another spring. The US patent to Uptegraff, Jr et al, issued on January 25, 1977, for Casing Construction For Pole Type Dielectric Containing Transformer discloses an operating stem carried for rotative movement by a bearing gasket secured to the underside of a cover. A spring is carried on the stem. The US patent to Kushman, et al, US-A-4,109,819, issued on August 29, 1978, for Explosion Vent and Method of Venting discloses a quick-release vent for releasing a rapid pressure buildup with a storage bin. The US patent to Kellogg, US-A-4 339 054, issued on July 13, 1982, for Pressure Relieved Plug And Socket Cleanout Assembly discloses a pressure relief valve mounted in a plug and is manually operated to vent excess pressure from a receptacle. An object of the present invention is to provide a bulk material container or the like with a manhole cover having a pressure relief valve thereon in which the application of the retaining force to secure the relief valve to a manhole cover does not adversely effect the seating and the sealing of the relief valve. An embodiment of the invention provides a bulk material container or the like having a manhole cover with a pressure relief valve in which a resilient spacer ring is disposed between a valve seat of a pressure relief valve and a support structure for a spring of the pressure relief valve, which spring urges a valve plate of the pressure relief valve toward the valve seat. A preferred embodiment provides a bulk material container or the like having a manhole cover with a vacuum passage in which vacuum relief apertures are formed through a backing plate of the pressure relief valve for the manhole cover, the vacuum relief apertures are adaptable for communicating with the fluid in the container and with the atmosphere, and a disc closes the vacuum relief apertures until displaced when the fluid pressure of the fluid within the container is less than the atmospheric pressure, the disc then moves away from the closure state of the vacuum relief apertures to provide a path for the air under atmospheric pressure to flow into the container through the vacuum relief apertures. Another preferred embodiment of the present invention provides a bulk material container or the like with a manhole cover having a pressure and vacuum relief valve in which the valve opening is increased beyond the initial opening for pressure and vacuum relief to accommodate an increased volume of fluid. A plate valve for pressure and vacuum relief may have limited clearance in the initial pressure and vacuum relief, because the constant of a spring does not allow the plate valve to open with a great enough expanse to pass the desired high volume of fluid. By employing a temperature activated pin or bolt, the plate valve moves to increase the valve opening, thus enabling the passing of an increased volume of fluid. A feature of the present invention is that a hinge for pivoting the pressure relief valve to the top of the manhole cover can be disposed at any selected location on the top wall of the manhole cover without adversely effecting the seating and sealing of the relief valve. Another feature of the present invention is the ability to maintain a relatively constant space between the valve seat of the pressure relief valve of the manhole cover and a compression spring support of the pressure relief valve regardless of the distortion of the manhole cover so as not to adversely effect the seating and sealing of the relief valve. Another feature of the present invention is that a single long lever for a locking mechanism can be employed to apply a restraining force to secure a pressure relief valve to a manhole cover without adversely effecting the seating and sealing of the relief valve. Reference is now made to the accompanying drawings wherein: Figure 1 is an elevation view of a bulk material container with a manhole cover having a pressure relief valve embodying the present invention. Figure 2 is an enlarged, fragmentary top view of the bulk material container shown in Figure 1. Figure 3 is an enlarged vertical sectional view taken along line 3-3 of Figure 2. Figure 4 is a vertical sectional view of a modification of a pivotal member of a latch employed in the bulk material container shown in Figures 1-3 under normal operating conditions. Figure 5 is a vertical sectional view of the pivotal member of the latch shown in Figure 4 illustrating the separation of the sections of the pivotal member of the latch after the melting of a melting alloy. DESCRIPTION OF THE PREFERRED EMBODIMENTS Illustrated in Figures 1-3 is a bulk material container 10 with a manhole cover 15 having a relief valve 20. The manhole cover 15 is disposed over a manhole opening 21 formed in the top wall 22 of the shell 10a of the container 10. The relief valve 20 includes a check or poppet valve 25 which opens to vent fluid pressure of fluid within the shell 10a of the container 10 exceeding a prescribed pressure to atmosphere. The relief valve 20 also includes a vacuum vent 30 which opens for air under atmospheric pressure or ambient pressure to flow into the shell 10a of the container 10 when the fluid pressure of fluid within the shell 10a of the container 10 is less than atmospheric pressure. While the exemplary embodiment makes reference to a container, it is to be understood that the inventive concepts of the present invention are equally applicable to a tanker truck with a manhole cover or a bin with a manhole cover. In the exemplary embodiment of the present invention, a suitable locking ring 31 secures the manhole cover 15 to the top wall 22 of the container 10 by gripping the wall of the top wall 22 surrounding the manhole opening 21 and by gripping the perimetric wall of the manhole cover 15. In the exemplary embodiment, the lock ring 31 is split so that confronting free ends thereof may be drawn toward one another to tighten the lock ring for gripping relation with the manhole cover 15 and the top wall 22 of the container 10 or may be drawn apart for loosening the lock ring to disengage the manhole cover 15 and the top wall 22 of the container 10 through the action of a nut and bolt arrangement 32. While a nut and bolt arrangement 32 is illustrated, other suitable arrangements may be employed equally as well, such as clamping forms of barrel lock rings. In the exemplary embodiment, gasket ring 33, such as a neoprene, is fixed to the underside of the manhole cover 15 below the perimetric wall thereof and is adapted for sealing engagement with the top wall of the container 10 surrounding the manhole opening 21. While the gasket ring 33 is illustrated as fixed to the manhole cover 15, it is apparent that it can be so fixed by a variety of different well-known procedures or may be shipped loosely in place. The manhole cover 15 also includes a restraining mechanism or a latch 35 for pivotally securing the relief valve 20 to the manhole cover 15. The latch 35 includes transversely spaced ears 36 which are secured to the top of the manhole cover 15. A latch plate 37 of the latch 35 is formed with a transversely disposed bore therethrough at one end thereof. A pivot pin 39 passes through the ears 36 and the bore formed through the plate 37 formed at the one end of the latch plate 37. Thus, the latch plate 37 is pivotally attached to the manhole cover 15. (See solid and dotted lines in Figure 3.) At the other end of the latch plate 37 is a locking flange 40 which is recessed in the latch plate 37. Fixed to the top wall of the manhole cover 15 are transversely spaced ears 41. Pivotally connected to the ears 41 through a pivot pin 42 is a pivotal member 43. At the top of the pivotal member 43 is pivotally attached a bifurcated cam locking lever 45 through a pivot pin 46'. The cam locking lever 45 is pivotally actuated to lockingly engage the recessed locking flange 40 (shown in solid line in Figure 3) or to release the recessed locking flange 40 from locking engagement (shown in dotted line in Figure 3). Formed in the latch plate 37 is a centrally located opening in which is disposed a retaining member or bolt 46 of the relief valve 20. The stem of the bolt 46 receives a compression coil spring 50 of the relief valve 20. A nut 51 is threaded onto the stem of the bolt 46. Formed in the manhole cover 15 is an opening 52 that is surrounded by an annular wall 53. The annular wall 53 defines an annular valve seat 55 for the relief valve 20. Displaceably engaging the annular valve seat 55 is a backing valve plate 60. The underside of the backing valve plate 60, which is adapted to engage the annular valve seat 55, is a resilient spacer sealing ring or gasket 61. In the exemplary embodiment, the resilient spacer sealing ring 61 is made of neoprene and when the sealing ring 61 engages the valve seat 55, there is sealing engagement therebetween. The compression spring 50 interengages the latch plate 37 and the backing valve plate 60. The nut 51 is disposed below the backing valve plate 60, while the head of the bolt 46 is disposed above the latch plate 37. Secured to the underside of the latch plate 37 by weldments is a reinforcing ring 65. When the latch plate 37 is latched to the manhole cover by the cam latching lever 45, the bottom wall of the reinforcing ring 65 engages the top of the manhole cover 15. Pivotal movement of the latch plate 37 imparts pivotal movement to the reinforcing ring 65. Formed in the reinforcing ring 65 are angularly spaced openings 66''. When the fluid pressure from the fluid in the shell 10a of the container 10 exceeds a predetermined magnitude, the fluid pressure overcomes the urgency of the spring 50. As a consequence thereof, the backing valve plate 60 is moved away from the valve seat 55. Fluid under pressure within the container 10 is vented through the opening 52 and through the openings 66'' to be vented to atmosphere. Thus, the relief valve 20 functions as a pressure relief valve. This action continues until the fluid pressure within the shell 10a of the container 10 is below the predetermined magnitude, at which time, the spring 50 urges the backing valve plate 60 into sealing engagement with the valve seat 55. The fluid pressure at which the backing valve plate 60 is displaced from the valve seat 55 to open the pressure relief valve 15 is determined by the spring constant of the spring 50 and not by the location of the nut 51 on the stem of the bolt 46. More specifically, the pressure exerted by the spring 50 on the plate 60 is a function of the spring constant of the spring 50. The tightening of the nut 51 on the bolt 46 reduces the space between the cover 37 and the seat 55. Hence, the pressure required to lift the plate 60 from the seat 55 is controlled by the constant of the spring 50. By virtue of the resilient spacer ring 61 between the valve seat 55 and the support structure for the pressure applying spring 50, the space between the support structure for the spring 50 and the valve seat 55 will remain constant when the relief valve 20 is latched to the manhole cover 15 by the restraining action of the latch mechanism 35, regardless of any distortion to the manhole cover 15 by the restraining action in latching the pressure relief valve 20 to the manhole cover 15. The backing valve plate 60 provides the support structure for the coil spring 50. By maintaining the space between the valve seat 55 and the support structure for the spring 50 constant, the adverse effect of the distortion of the manhole cover 15 on the seating and sealing of the backing plate 60 on the valve seat 55 is reduced. Thus, the pivotal connection for the latch plate 37 can be located at various selected places along the manhole cover 15 and the single long cam locking lever 45 can be employed as the locking member. In order for ambient air or air under atmospheric pressure to enter the shell 10a of the container 10 when the fluid pressure from the fluid in the shell 10a of the container 10 is less than atmospheric pressure, vacuum relief apertures 75 are formed through the backing valve plate 60 and aligned vacuum relief apertures 75' are formed through the resilient spacer ring 61. The vacuum relief apertures 75 and 75', in the preferred embodiment, are disposed equal angular distances apart and at equal radial distances from the center line of the relief valve 20, as defined by the axes of the bolt 46, the backing valve plate 60 and the spacer ring 61. Disposed below the spacer ring 61 and above the nut 51 is a rigid vacuum relief backing disc 66 that is received by the bolt 46. A neoprene O-ring 66' is disposed between the nut 51 and the rigid vacuum relief backing disc 66. Disposed between the spacer ring 61 and the rigid vacuum relief backing disc 66 is a yieldable annular flap 70 that is also received by the bolt 46. The nut 51 retains the vacuum relief backing disc 66 and the annular flap 70 in a fixed position along the axis of the bolt 46. The radial distance of the flap 70 is greater than the radial distance of the vacuum relief apertures 75'. The radial extent of the vacuum relief backing disc 66 is great enough to retain the flap 70 firmly in position but insufficient to extend below the vacuum relief apertures 75 or interfere with the flapping action of the marginal perimeter 70a of the flap 70. Thus, the marginal perimeter 70a of the flap 70 is capable of being displaced away from the spacer ring 61. When the fluid pressure of the fluid in the container 10 is equal to or greater than atmospheric pressure, the flap 70 is firmly urged against the spacer ring 61 by the fluid pressure in the container 10 to seal the adjacent ends of the vacuum relief apertures 75. When the fluid pressure of the fluid in the container 10 is less than atmospheric pressure, the marginal perimeter 70a of the flap 70 is displaced from the spacing ring 61 by the atmospheric pressure exceeding the fluid pressure in the shell 10a of the container 10. Thus, air under atmospheric pressure enters the shell 10a of the container 10 over the following path to lessen the degree of vacuum in the shell 10a of the container 10: openings 66'' of the reinforcing ring 65, space between the latch plate 37 and the backing valve plate 60, vacuum relief apertures 75, and vacuum relief apertures 75'. This action continues until the fluid pressure within the container is at least equal to atmospheric pressure. The pivotal movement of the latch plate 37 about the axis of the pin 39 imparts pivotal movement therewith to the bolt 46, the spring 50, the backing valve plate 60, the spacer ring 61, the reinforcing ring 65, the vacuum relief disc 66 and the flap 70. Illustrated in Figure 4 is a fusible device or a pivotal member 43' for the latch 35 which is a modification of the pivotal member 43 shown in Figures 1-3 for the latch 35. The pivotal member 43' is separated into two sections 43'a and 43'b disposed in contiguous relation. The section 43'a receives the pivot pin 46' (figures 2, 3 and 4) and the section 43'b receives the pivotal pin 42. Formed in the confronting ends of the sections 43'a and 43'b are suitable complementary openings 151 and 152. Seated in the openings 151 and 152 is a suitable threaded pin or cap screw 155. The walls surrounding the opening 151 are in threaded engagement with the screw 155 to hold the screw 155 in a fixed position therein. Disposed within the opening 152 about the portion of the cap screw 155 received therein is a melting alloy 160. The melting alloy 160, while solid, holds the screw 155 in a fixed position within the opening 152. The screw 155 and the melting alloy 160 serve to maintain the pivotal member 43' in contiguous relation for functioning as a unitary structure in the manner the pivotal member 43 functions as part of the latch 35. The melting alloy 160 is a well-known product commonly used in fusible devices. A supplier of such melting alloys is Federated Metals of Union City, California. The melting temperature for the melting alloy 160 may be in the range of 104.4°C-148.9°C (220°F-300°F) or any other suitable range. In the exemplary embodiment, the melting alloy 160 melts at 104.4°C (220°F). When the temperature surrounding the pivotal member 43' reaches 104.4°C (220°F), in the exemplary embodiment, the sections 43'a and 43'b are separable and do not function as a unitary structure, because the melting alloy 160 is melted and no longer retains the screw 155 in a fixed position in the opening 152. As a consequence thereof, the sections 43'a and 43'b become spaced further part (Figure 5) to enable the latch plate 37 to be pivotally lifted to a greater extent by the fluid pressure of the bulk material in the shell 10a (Figure 3). The pivotal lifting of the latch plate 37 raises the valve plate 60, the spacer member 61 the yieldable member 70a, and the relief backing plate 66 to open the opening 52 in the wall 53 of the shell 10a to a greater extent. The volume of the fluid of the bulk material in the shell 10a is thereby vented to atmosphere at a greater rate. Thus, the fusible device 43' of the latch 35 serves as part of the relief valve 20. The melting alloy 160 tends to be removed from the pivotal member 43' via the space between the section 43'b and the screw 151 under the urgency of the screw head 155a (Figure 5).

Claims: A manhole cover (15) for a bulk material container (10), said manhole cover (15) being formed with an opening (52) therethrough and comprising: a valve seat (55) surrounding said opening (52) in said manhole cover (15); a movable valve plate (60) disposed over said opening (52) in said manhole cover (15), said valve plate (60) being formed with a first central opening; a resilient spacer member (61) secured to said valve plate (60) for movement therewith and disposed in displaceable engagement with said valve seat (55) for sealing engagement therewith, said spacer member (61) being formed with a second central opening aligned with said first central opening; a retaining member (46) received by said first central opening of said movable valve plate (60) and said second central opening of said spacer member (61); a spring (50) surrounding said retaining member (46) in engagement with said movable valve plate (60) for urging said movable valve plate (60) and said spacer member (61) toward said valve seat (55) for sealing engagement between said spacer member (61) and said valve seat (55); and a latch (35) attached to said cover (15), said latch (35) having a third central opening therethrough aligned with said first and second central opening for receiving said retaining member (46), said latch (35) supporting said retaining member (46), and said latch (35) supporting by means of said retaining member (46) said valve plate (60) and said spring (50) surrounding said retaining member (46), said spacer member (61) being disposed between said valve seat (55) and said valve plate (60), said spring (50) surrounding said retaining member (46) being disposed in engagement with said movable valve plate (60), for urging a relatively constant seating engagement and sealing engagement between said valve seat (55) and said spacer member (61) in the event of distortion of said cover (15), and said valve plate (60) and said spacer member (61) being displaced from said valve seat (55) against the urgency of said spring (50) in the event fluid pressure applied against said spacer member (61) and said valve plate (60) exceeds a predetermined magnitude of fluid pressure. A manhole cover (15) as claimed in Claim 1 and further characterized by said valve plate (60) and said spacer member (61) being formed with aligned vacuum relief apertures (75, 75'), and the manhole cover further comprising a relief backing plate (66); said relief backing plate (66) being formed with a fourth central opening aligned with said first, second and third central openings and received by said retaining member (46); and a yieldable member (70) disposed between said resilient spacer member (61) and said relief backing plate (66) in sealing engagement with said spacer member (61) when the fluid pressure applied against said yieldable member (70) in one direction is at least atmospheric pressure, said yieldable member (70) being formed with a fifth central opening aligned with said first, second, third and fourth central openings and received by said retaining member (46), said yieldable member (70) extending outwardly from said retaining member (46) a distance greater than the location of said aligned relief apertures (75, 75') for closure of said aligned relief apertures (75, 75'), said relief backing plate (66) extending outwardly from said retaining member (46) a distance lesser than the outermost location of said aligned relief apertures (75, 75'), said yieldable member (70) maintaining a closure of said aligned relief apertures (75, 75') while fluid pressure applied to said yieldable member (70) in said one direction is at least atmospheric pressure, said yieldable member (70) being displaced away from said spacer member (61) in the event fluid pressure applied to said yieldable member (70) in said one direction is less than atmospheric pressure for air under atmospheric pressure to pass through said aligned relief apertures (75,75'). A manhole cover (15) as claimed in Claim 1 or Claim 2 and comprising a reinforcing member (65) disposed between said cover (15) and said latch (35), said reinforcing means (65) being formed with apertures (66'') for the passage of fluid under pressure to atmosphere and the passage of air under atmospheric pressure through said relief apertures (75, 75'). A manhole cover (15) as claimed in Claim 2 wherein said latch (35) at one end thereof is pivotally (36, 39) attached to said cover (15), said latch (35) at the other end thereof includes a restraining mechanism (40, 41, 42, 43, 45, 46') connected to said cover (15) for removably locking said latch (35) over said opening (52) with said spacer member (61) in sealing engagement with said valve seat (55), pivotal movement of the latch (35) moves in unison therewith said valve plate (60), said retaining member (46), said spring (50), said spacer member (61), said relief backing plate (66) and said yieldable member (70). A manhole cover (15) as claimed in Claim 3 or in Claim 4 wherein said reinforcing member (65) is secured to said latch (35) and the pivotal movement of said latch (35) imparts therewith movement to said reinforcing member (65). A manhole cover (15) for a bulk material container (10) as claimed in Claim 1 wherein said latch (35) at one end thereof is pivotally attached to said cover (15), said latch (35) at the other end thereof includes a restraining mechanism (40, 41, 42, 43, 45, 46') connected to said cover for (15) removably locking said latch (35) over said opening (52) of said cover (15) with said spacer member (61) in sealing engagement with said valve seat (55), further characterized by said restraining mechanism (40, 41, 42, 43, 45, 46') comprising a fusible device (43') meltable at a predetermined temperature for enabling said latch (35) to pivotally move away from said valve seat (55), the pivotal movement of said latch (35) away from said valve seat (55) moves said valve plate (60) and said spacer member (61) away from said valve seat (55) for enabling fluid under pressure to vent to atmosphere. A manhole cover (15) for a bulk material container (10) as claimed in Claim 4 wherein said restraining mechanism (40, 41, 42, 43, 45, 46') comprises a fusible device (43') meltable at a predetermined temperature for enabling said latch (35) to pivotally move away from said valve seat (55), the pivotal movement of said latch (35) away from said valve seat (55) moves therewith said valve plate (60), said spacer member (61), said relief backing plate (66) and said yieldable member (70). A manhole cover (15) for a bulk material container (10) as claimed in Claim 1 wherein said fusible device (43') comprises: a pivotal member (43') having separable sections (43'a, 43'b), each of said separable sections (43'a, 43'b) being formed with confronting openings (151, 152), a threaded element (155) received by said confronting openings (151, 152) of said pivotal member (43'), a portion of said threaded element (155) being fixedly disposed in one of said openings (151, 152), another portion of said threaded element (155) being disposed in the other of said openings (151, 152), and a melting alloy (160) disposed in said other opening (152) for retaining said threaded element (155) in said other opening (152) until said melting alloy (160) is melted at said predetermined temperature. A bulk container (10) having an opening (21) closed by a manhole cover as claimed in any preceding claim.

Inventors: COLEMAN CLARENCE
Applicants: FABRICATED METALS, INC.
Application year: 1988
Main classification: B65D90
IPC codes: B65D90