CA1093506A - Multi-section lifting boom - Google Patents
Multi-section lifting boomInfo
- Publication number
- CA1093506A CA1093506A CA346,322A CA346322A CA1093506A CA 1093506 A CA1093506 A CA 1093506A CA 346322 A CA346322 A CA 346322A CA 1093506 A CA1093506 A CA 1093506A
- Authority
- CA
- Canada
- Prior art keywords
- boom
- piston rod
- section
- deflection
- ram
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
TITLE
MULTI-SECTION LIFTING BOOM
INVENTOR
John L. GROVE
ABSTRACT
A lifting boom having three telescopic sections.
A hydraulic ram has a piston rod free end connected by a horizontal pin movable in guide slots at the rear of the base section. A deflection limiter is axially slidable on the piston rod, and is less high than the base section. The rear of the ram cylinder is pin connected by horizontal pins to the midsection, and has a transverse ram cylinder plate attached to it. Pull rods are connected to the deflection limiter and pass forwardly through the transverse plate, having detents at their forward ends beyond the transverse plates. A pair of chains extends from the base section forward and around sprockets at the rear of the mid-section, being attached to the rear of the fly section, a further chain extending thence forwardly and around a sprocket on the front end of the ram cylinder, and thence rearwardly to an anchor on the base section; the ram sprocket has a roller portion which rolls on the fly section bottom plate to support the ram cylinder. The heel of the fly section raises the ram forward end when the boom is extended and the sections are cocked or arched, limited by the roller engaging the bottom of the fly section top plate.
MULTI-SECTION LIFTING BOOM
INVENTOR
John L. GROVE
ABSTRACT
A lifting boom having three telescopic sections.
A hydraulic ram has a piston rod free end connected by a horizontal pin movable in guide slots at the rear of the base section. A deflection limiter is axially slidable on the piston rod, and is less high than the base section. The rear of the ram cylinder is pin connected by horizontal pins to the midsection, and has a transverse ram cylinder plate attached to it. Pull rods are connected to the deflection limiter and pass forwardly through the transverse plate, having detents at their forward ends beyond the transverse plates. A pair of chains extends from the base section forward and around sprockets at the rear of the mid-section, being attached to the rear of the fly section, a further chain extending thence forwardly and around a sprocket on the front end of the ram cylinder, and thence rearwardly to an anchor on the base section; the ram sprocket has a roller portion which rolls on the fly section bottom plate to support the ram cylinder. The heel of the fly section raises the ram forward end when the boom is extended and the sections are cocked or arched, limited by the roller engaging the bottom of the fly section top plate.
Description
~,~g;~
The present invention relates to a multi-section lifting boom, useful in such apparatus as cranes and aerial lift platforms.
The present invention has as an object the provision of a multi-section lifting boom in which a rotary member serves both as a support for a hydraulic ram and as a sprocket for a chain or cable which extends and retracts a boom section. Another object is the provision of a multi-section load lifting boom which permits limited buckling of the piston rod of the hydraulic ram or motor which extends and retracts the boom section. Another object is to provide such a boom in which the cocking of an outer section relieves strain on the piston rod of the hydraulic ram or motor.
I,ifting booms for cranes and aexial lift plat~orms typically are made;of multiple, extensible telescopic section6. Extention and retraction is effected by one or more hydraulic cylinders, or a combination of hydraulic cylinders and cable or chains trained over pulleys or sprockets.
When the booms are extended, and are under load, they tend to depart from a theoretical arrangement in which the boom sections are in alignment with each other. This is known as arching or cocking, and steps have been taken in the art to avoid harmful effects thereof.
Another problem which has been recognized is that if the boom sections cock relative to each other, there is a strain placed upon the hydraulic ram which extends and retracts the boom sections, leading to damage to the ram, such as occurs when the piston rod buckles under compressive loads, since it acts as a lony column, and also has the 5 01~
harmful effect of deteriorating the seals of t~e hydraulic ram. In addition, there have been proposals for providing great strength, with minimum utilization of metal.
Various relavent disclosures are present in the prior art. Thus, Sterner, U.S. Patent #3,736,710 discloses a four section telescopic crane boom which utilizes three single piston rams, one of which has the cylinder pin-connected at its rear end to a boom mid-section, and e~tending forwardly, the forward end of the cylinder resting on a slide-bearing arrangement, the piston rod extending rearwardly, and having its free end connected to the boom base section by a floating arrangement allowing the end of the piston rod to move transversely of the boom longitudinal axis.
Sakamoto, U.S.A. Patent #3,722,15~ discloses a construction in which the piston rod of the hydraullc ram of a multi-section telescopic boom has a buckle-preventing device slidable thereon, and comprising outwardly extending portions which movably engage with the inside sur~aces of the relavent boom section, such as with the bottom of the base section upper plate and the top of the base se~tion bottom plate. The piston rod is pin-connected to one section of the boom, and the cylinder is pin-connected to another section of the boom. This construction severely limits the amount of cocking of the boom sections which can be tolerated without damage to the hydraulic ram, and appears to actually increase the load of the hydraulic ram when the boom sections are in the cocked attitude, by virtue of the engagement o~ the buckle-preventing device continuously with the boom section.
Kollmann et al, U.S.A. Patent #3,715,039 discloses a telescopic boom having a plurality of boom sections, and a s03~
plurality of hydraulic rams in line, with the piston rod of one ram being pin-connected to ~he cylinder of an adjacent ram, and with a wheel structure mounted on the connecting pin, the wheel structure being supported by the boom section to thereby support the pin connection.
Hornagold, U.S.A. Patent # 3,837,502 discloses a lifting boom in which fixed detents are engaged by the piston rod of a hydraulic ram after some bending thereof.
There is provided herein a lifting boom which comprises three telescopic sections, which are linearly extensible and retractable. A single hydraulic ram is utili7ed, having a piston rod free end which is connected by a horizontal pin to the rear of the base section of the boom, the connection being a "floating" connection, since the horizontal pin is movable in generally vertical extending guide slots provided at the rear of the boom base section. A deflection limiting device is slidable alony the piston rod, and i8 l~ss high than the base section, the top of the deflec~ion limiter being spaced from the bottom of the boom top plate when the boom is not under load, but being in enga~ement therewith when the boom is extended and is under load~ The rear of the ram cylinder has a ram cylinder plate welded to it, and extending transversely of its axis, the plate comprising horizontal pins which pin-connect the plate and therefore the ram cylinder to the mid-section. Pull rods are provided for moving the deflection limiter, the rear ends of the pull rods extending through a transverse plate of the deflection limiter, having nuts on their rear end~, the pull rods passing forwardly through the transverse plate o~ the deflection limiter and through the ram cylinder plate. I'he forward ends of the 35C~6i pull rods have nuts or other detents thereon, so that when the hydraulic ram has been extended, the front face of the ram cylinder plate will engage the nuts or detents on the forward ends of the pull rods, and pull the deflection limiter along the piston rod of the hydraulic ram. A pair of chains extends from the forward end of the base section of the bottom plate thereof, rearwardly, passing around sprockets carried at the rear end of the mid-section, and is Y
attached to the rear of the fly section a second chain extends forwardly, passing around the forward end of the hydraulic ram. A combined sprocket and roller is carried by the forward end of the hydraulic ram, and the chain pas~es :~
on this sprocke~ and thence rearwardly to an anchor at the rear of the base section. The combined sprocket and roller rolls on the bottom plate of the fly section, to support the forward end of the ram cylinder, during the boom extension, and when ~ully extended the heel of the fly section engages the ram cylinder at the bottom of the forward end, rotating it on its pivots, rotation being limited by engagement of the roller with the top of the fly section, that is, the upper plate thereof. m is also serves to reduce buckling stresses on the piston rod.
The invention therefore contemplates a multi~section `~
lifting boom having at least two sections in telescopic relation and a hydraulic motor having a cylinder and piston rod each connected to one said section for extension and retraction of one said sect.ion relative to the other, and wherein said piston rod is subject to deflection when said hydraulic motor is extended and said boom is under load, ~0 means for limiting the deflection of said piston rod to a predetermined amount after initial deflection thereof when ~3351~
said motor is extended and said boom is under load, said deflection limiting means comprising means movable along said piston rod, and means actuated by said motor cylinder for moving said deflection limiting means along said piston rod.
IN THE DRAWINGS
Figure 1 is a vertical cross sectional view of a lifting boom in accordance with the present invention.
Figure 2 is a cross sectional view taken on the line
The present invention relates to a multi-section lifting boom, useful in such apparatus as cranes and aerial lift platforms.
The present invention has as an object the provision of a multi-section lifting boom in which a rotary member serves both as a support for a hydraulic ram and as a sprocket for a chain or cable which extends and retracts a boom section. Another object is the provision of a multi-section load lifting boom which permits limited buckling of the piston rod of the hydraulic ram or motor which extends and retracts the boom section. Another object is to provide such a boom in which the cocking of an outer section relieves strain on the piston rod of the hydraulic ram or motor.
I,ifting booms for cranes and aexial lift plat~orms typically are made;of multiple, extensible telescopic section6. Extention and retraction is effected by one or more hydraulic cylinders, or a combination of hydraulic cylinders and cable or chains trained over pulleys or sprockets.
When the booms are extended, and are under load, they tend to depart from a theoretical arrangement in which the boom sections are in alignment with each other. This is known as arching or cocking, and steps have been taken in the art to avoid harmful effects thereof.
Another problem which has been recognized is that if the boom sections cock relative to each other, there is a strain placed upon the hydraulic ram which extends and retracts the boom sections, leading to damage to the ram, such as occurs when the piston rod buckles under compressive loads, since it acts as a lony column, and also has the 5 01~
harmful effect of deteriorating the seals of t~e hydraulic ram. In addition, there have been proposals for providing great strength, with minimum utilization of metal.
Various relavent disclosures are present in the prior art. Thus, Sterner, U.S. Patent #3,736,710 discloses a four section telescopic crane boom which utilizes three single piston rams, one of which has the cylinder pin-connected at its rear end to a boom mid-section, and e~tending forwardly, the forward end of the cylinder resting on a slide-bearing arrangement, the piston rod extending rearwardly, and having its free end connected to the boom base section by a floating arrangement allowing the end of the piston rod to move transversely of the boom longitudinal axis.
Sakamoto, U.S.A. Patent #3,722,15~ discloses a construction in which the piston rod of the hydraullc ram of a multi-section telescopic boom has a buckle-preventing device slidable thereon, and comprising outwardly extending portions which movably engage with the inside sur~aces of the relavent boom section, such as with the bottom of the base section upper plate and the top of the base se~tion bottom plate. The piston rod is pin-connected to one section of the boom, and the cylinder is pin-connected to another section of the boom. This construction severely limits the amount of cocking of the boom sections which can be tolerated without damage to the hydraulic ram, and appears to actually increase the load of the hydraulic ram when the boom sections are in the cocked attitude, by virtue of the engagement o~ the buckle-preventing device continuously with the boom section.
Kollmann et al, U.S.A. Patent #3,715,039 discloses a telescopic boom having a plurality of boom sections, and a s03~
plurality of hydraulic rams in line, with the piston rod of one ram being pin-connected to ~he cylinder of an adjacent ram, and with a wheel structure mounted on the connecting pin, the wheel structure being supported by the boom section to thereby support the pin connection.
Hornagold, U.S.A. Patent # 3,837,502 discloses a lifting boom in which fixed detents are engaged by the piston rod of a hydraulic ram after some bending thereof.
There is provided herein a lifting boom which comprises three telescopic sections, which are linearly extensible and retractable. A single hydraulic ram is utili7ed, having a piston rod free end which is connected by a horizontal pin to the rear of the base section of the boom, the connection being a "floating" connection, since the horizontal pin is movable in generally vertical extending guide slots provided at the rear of the boom base section. A deflection limiting device is slidable alony the piston rod, and i8 l~ss high than the base section, the top of the deflec~ion limiter being spaced from the bottom of the boom top plate when the boom is not under load, but being in enga~ement therewith when the boom is extended and is under load~ The rear of the ram cylinder has a ram cylinder plate welded to it, and extending transversely of its axis, the plate comprising horizontal pins which pin-connect the plate and therefore the ram cylinder to the mid-section. Pull rods are provided for moving the deflection limiter, the rear ends of the pull rods extending through a transverse plate of the deflection limiter, having nuts on their rear end~, the pull rods passing forwardly through the transverse plate o~ the deflection limiter and through the ram cylinder plate. I'he forward ends of the 35C~6i pull rods have nuts or other detents thereon, so that when the hydraulic ram has been extended, the front face of the ram cylinder plate will engage the nuts or detents on the forward ends of the pull rods, and pull the deflection limiter along the piston rod of the hydraulic ram. A pair of chains extends from the forward end of the base section of the bottom plate thereof, rearwardly, passing around sprockets carried at the rear end of the mid-section, and is Y
attached to the rear of the fly section a second chain extends forwardly, passing around the forward end of the hydraulic ram. A combined sprocket and roller is carried by the forward end of the hydraulic ram, and the chain pas~es :~
on this sprocke~ and thence rearwardly to an anchor at the rear of the base section. The combined sprocket and roller rolls on the bottom plate of the fly section, to support the forward end of the ram cylinder, during the boom extension, and when ~ully extended the heel of the fly section engages the ram cylinder at the bottom of the forward end, rotating it on its pivots, rotation being limited by engagement of the roller with the top of the fly section, that is, the upper plate thereof. m is also serves to reduce buckling stresses on the piston rod.
The invention therefore contemplates a multi~section `~
lifting boom having at least two sections in telescopic relation and a hydraulic motor having a cylinder and piston rod each connected to one said section for extension and retraction of one said sect.ion relative to the other, and wherein said piston rod is subject to deflection when said hydraulic motor is extended and said boom is under load, ~0 means for limiting the deflection of said piston rod to a predetermined amount after initial deflection thereof when ~3351~
said motor is extended and said boom is under load, said deflection limiting means comprising means movable along said piston rod, and means actuated by said motor cylinder for moving said deflection limiting means along said piston rod.
IN THE DRAWINGS
Figure 1 is a vertical cross sectional view of a lifting boom in accordance with the present invention.
Figure 2 is a cross sectional view taken on the line
2-2 of Figure 1.
Figure 3 is a cross sectional view taken the line 3-3 of Figure 1.
Figure 4 is a view of the boom of Figure 1 in arched condition.
Referring now to the drawings, wherein like or corresponding reference numerals are used to designate like or corresponding parts through out the several views, there is shown in Figure 1 a multi-section lifting boomlsuitable for cranes and aerial lift platfo~ms, designated 10, and ~ -comprising a base section 11, a mid-section 12 and a fly section 13. These sections may take various cross sectional shapes, but in the herein disclosed preferred embodiment, each section is a generally hollow rectangle in transverse cross section, as is apparent ~rom Figures 2 and 3.
A hydraulic ram 20 is provided, ram 20 being in a position which is inverted from that which is normal; thus, the ram 20 includes the hydraulic cylinder 21 which extends forwardly, and the piston rod 22, which extends rearwardly.
At its rear end, piston rod 22 has a transverse pin 23, which is in a horizontal plane, and the ends of which are positioned in a guide 24 which permit the pin 23 and ~9~
therefore the end of the piston rod 22 to have limited movement in a vertical plane transverse to the boom longltudinal axis.
A ram cylinder plate 26 is welded at the rear end of the cylinder 21 of`hydraulic ram 20, the hydraulic ram plate 26 including transversely extending pins 27, which are horizontal, and which are journalled in suitable openings in the mid-section 12.
A device 30 is provided for permitting limited movement or buckling of piston rod 22, and comprises, as shown in Figure 2, a transverse limiter plate 31 having an aperture therein through which the piston rod 22 passes, there being sliding engagement between transverse limiter plate 31 and the exterior of piston rod 22. A pair o~
vertical limiter plates 32 and 33 are connected to the transverse limiter plate 31, and as is clearly shown in Figure 2, these vertical limiter plates 32 and 33 stop short o~ engagement with the bottom of the top plate o~ boom base section 11 in the condition in which the boom is not loaded.
Pull rod~ 34 and 35 extend generally axially, there being provided at the forward ends of pull rods 34 and 35 detents 34a and 35b, which may take the form of nuts.` At their rear ends, the rods 34 and 35 pass through apertures in the transverse limiter plate 31, where enlargements, such as the nuts 34b and 35b are provided. When the hydraulic ram 20 is extended to the right, the ram cylinder plate 26 moves with it, moving the mid-section 12, and the ram cylinder plate 26 passes along the pull rods 34 and 35 until the front thereo~
engages the rear of the nuts or detents 34a and 35a, after which the piston ~od buckle limiter 30 i8 pulled along the piston rod 22. The dimensional relationships are such that 5~
in the fully extended position of the hydraulic ram 20, the piston rod buckle limiter 30 is approximately at the mid-point of the piston rod 22.
A combination roller-sprocket 40 is provided, supported on a support 41 which extends forwardly from the forward end of a cylinder 21, and carries an axle 42.
Preferably, the support 41 is bifurcated. The outer surface of the combination xollex-sprocket 40 has paralle] wheels which serve as a roller, being in engagement with the upper surface of the bottom plate of the fly section 13 during initial extension o~ the boom. The combination roller-sprocket 40 has the sprocket part thereof slightly lesser effective diameter than the parallel wheels forming the roller, as indicated by dashed lines, to accommodate the thickness of a chain.
A pair of chains 43 extend rearwardly from an anchor 44 which is positioned at the front end of the bottom plate of the base section 11. The chains 43 pass around sprockets 45 carried at the rear of the mid-section 12, and thence to an anchor 46 on the rear of the fly section 13. A chain 47 passes from the anchor 46 fcrwardly, and around the combirlation roller-sprocket 40, and thence extends rearwardly to the anchor 48 which is located on the upper plate of the boom base section 11.
When the boom 10 is extended and is under load as shown in Figure 4, arching ox cocking of the boom sections relative to each other will not result in harmful effect to the hydraulic ram 20, due to the floating connection of the free end of the piston rod 22, and the pin connection of the cylinder 21 to the boom mid~section 120 In addition, the forward end of the cylinder 21 is supported by thé
combination roller-sprocket 40, which supports the forward end of the hydraulic ram 20, and serves as a guide for the chain 47. In addition, the arching or cocking of the sections will not damage the hydraulic ram 20~ and particularly the piston rod 22 thereof, because the piston rod 22 will be permitted a limited, predetermined amount of buckling, due to the spacing of the upper end of the vertical limiter plates 32 and 33 from the bottom surface of the top plate of the boom base section 11, this spacing permitting arching or cocking without transmission to the piston rod 22 of undesirable loads, and without providing a harmful effect on the seals where the piston rod 22 passes through the left or inner end of the cylinder 21.
With further reference to the condition of the boom as shown in Figure 4, in which the boom sections are fully extended, and are under load, arching or cocking as illustrated therein will occur. The heel of the boom fly section 13, or more particularly the anchor ~6 which is at the heel thereof will engage the cylinder 21 of the hydraulic ram 20 at the bottom of the forward end ther~of.
The heel of the ~ly section is that portion which is at the rear o~ the fly section. This will rotate the cylinder 21 about the axis provided by the pins 27, the rotation being to a limited amount as determined by the engagement of the combination roller-sprocket 40 with the bottom o~ the top plate of the ~ly section 13. As will be understood, the diameter of the roller-sprocket 40 is slightly less than the vertical height of the space provided by the fly section 13, and more particularly is slightly less than the space between the top of the bottom plate of fly section 13. 'rhis construction will thereby serve to enable the cylinder 21 to )9~5~
be rotated in a direction to reduce the stresses tending to buckle the piston rod 22, and thereby further serves to avoid harmful effects of arching or cocking of the boom sections when extended and loaded on the ram 20, including particularly the piston rod 22 thereof.
It will be obvious to those skilled in the art that various changes may be made without departing from the spirit of the invention, and therefore the invention is not limited to what is shown in the drawings and described in the specification but only as indicated in the appended claims.
Figure 3 is a cross sectional view taken the line 3-3 of Figure 1.
Figure 4 is a view of the boom of Figure 1 in arched condition.
Referring now to the drawings, wherein like or corresponding reference numerals are used to designate like or corresponding parts through out the several views, there is shown in Figure 1 a multi-section lifting boomlsuitable for cranes and aerial lift platfo~ms, designated 10, and ~ -comprising a base section 11, a mid-section 12 and a fly section 13. These sections may take various cross sectional shapes, but in the herein disclosed preferred embodiment, each section is a generally hollow rectangle in transverse cross section, as is apparent ~rom Figures 2 and 3.
A hydraulic ram 20 is provided, ram 20 being in a position which is inverted from that which is normal; thus, the ram 20 includes the hydraulic cylinder 21 which extends forwardly, and the piston rod 22, which extends rearwardly.
At its rear end, piston rod 22 has a transverse pin 23, which is in a horizontal plane, and the ends of which are positioned in a guide 24 which permit the pin 23 and ~9~
therefore the end of the piston rod 22 to have limited movement in a vertical plane transverse to the boom longltudinal axis.
A ram cylinder plate 26 is welded at the rear end of the cylinder 21 of`hydraulic ram 20, the hydraulic ram plate 26 including transversely extending pins 27, which are horizontal, and which are journalled in suitable openings in the mid-section 12.
A device 30 is provided for permitting limited movement or buckling of piston rod 22, and comprises, as shown in Figure 2, a transverse limiter plate 31 having an aperture therein through which the piston rod 22 passes, there being sliding engagement between transverse limiter plate 31 and the exterior of piston rod 22. A pair o~
vertical limiter plates 32 and 33 are connected to the transverse limiter plate 31, and as is clearly shown in Figure 2, these vertical limiter plates 32 and 33 stop short o~ engagement with the bottom of the top plate o~ boom base section 11 in the condition in which the boom is not loaded.
Pull rod~ 34 and 35 extend generally axially, there being provided at the forward ends of pull rods 34 and 35 detents 34a and 35b, which may take the form of nuts.` At their rear ends, the rods 34 and 35 pass through apertures in the transverse limiter plate 31, where enlargements, such as the nuts 34b and 35b are provided. When the hydraulic ram 20 is extended to the right, the ram cylinder plate 26 moves with it, moving the mid-section 12, and the ram cylinder plate 26 passes along the pull rods 34 and 35 until the front thereo~
engages the rear of the nuts or detents 34a and 35a, after which the piston ~od buckle limiter 30 i8 pulled along the piston rod 22. The dimensional relationships are such that 5~
in the fully extended position of the hydraulic ram 20, the piston rod buckle limiter 30 is approximately at the mid-point of the piston rod 22.
A combination roller-sprocket 40 is provided, supported on a support 41 which extends forwardly from the forward end of a cylinder 21, and carries an axle 42.
Preferably, the support 41 is bifurcated. The outer surface of the combination xollex-sprocket 40 has paralle] wheels which serve as a roller, being in engagement with the upper surface of the bottom plate of the fly section 13 during initial extension o~ the boom. The combination roller-sprocket 40 has the sprocket part thereof slightly lesser effective diameter than the parallel wheels forming the roller, as indicated by dashed lines, to accommodate the thickness of a chain.
A pair of chains 43 extend rearwardly from an anchor 44 which is positioned at the front end of the bottom plate of the base section 11. The chains 43 pass around sprockets 45 carried at the rear of the mid-section 12, and thence to an anchor 46 on the rear of the fly section 13. A chain 47 passes from the anchor 46 fcrwardly, and around the combirlation roller-sprocket 40, and thence extends rearwardly to the anchor 48 which is located on the upper plate of the boom base section 11.
When the boom 10 is extended and is under load as shown in Figure 4, arching ox cocking of the boom sections relative to each other will not result in harmful effect to the hydraulic ram 20, due to the floating connection of the free end of the piston rod 22, and the pin connection of the cylinder 21 to the boom mid~section 120 In addition, the forward end of the cylinder 21 is supported by thé
combination roller-sprocket 40, which supports the forward end of the hydraulic ram 20, and serves as a guide for the chain 47. In addition, the arching or cocking of the sections will not damage the hydraulic ram 20~ and particularly the piston rod 22 thereof, because the piston rod 22 will be permitted a limited, predetermined amount of buckling, due to the spacing of the upper end of the vertical limiter plates 32 and 33 from the bottom surface of the top plate of the boom base section 11, this spacing permitting arching or cocking without transmission to the piston rod 22 of undesirable loads, and without providing a harmful effect on the seals where the piston rod 22 passes through the left or inner end of the cylinder 21.
With further reference to the condition of the boom as shown in Figure 4, in which the boom sections are fully extended, and are under load, arching or cocking as illustrated therein will occur. The heel of the boom fly section 13, or more particularly the anchor ~6 which is at the heel thereof will engage the cylinder 21 of the hydraulic ram 20 at the bottom of the forward end ther~of.
The heel of the ~ly section is that portion which is at the rear o~ the fly section. This will rotate the cylinder 21 about the axis provided by the pins 27, the rotation being to a limited amount as determined by the engagement of the combination roller-sprocket 40 with the bottom o~ the top plate of the ~ly section 13. As will be understood, the diameter of the roller-sprocket 40 is slightly less than the vertical height of the space provided by the fly section 13, and more particularly is slightly less than the space between the top of the bottom plate of fly section 13. 'rhis construction will thereby serve to enable the cylinder 21 to )9~5~
be rotated in a direction to reduce the stresses tending to buckle the piston rod 22, and thereby further serves to avoid harmful effects of arching or cocking of the boom sections when extended and loaded on the ram 20, including particularly the piston rod 22 thereof.
It will be obvious to those skilled in the art that various changes may be made without departing from the spirit of the invention, and therefore the invention is not limited to what is shown in the drawings and described in the specification but only as indicated in the appended claims.
Claims (6)
1. A multi-section lifting boom having at least two sections in telescopic relation and a hydraulic motor having a cylinder and piston rod each connected to one said section for extension and retraction of one said section relative to the other, and wherein said piston rod is subject to deflection when said hydraulic motor is extended and said boom is under load, means for limiting the deflection of said piston rod to a predetermined amount after initial deflection thereof when said motor is extended and said boom is under load, said deflection limiting means comprising means movable along said piston rod, and means actuated by said motor cylinder for moving said deflection limiting means along said piston rod.
2. The telescopic boom of claim 1, wherein said deflection limiting means comprises means slidable on said piston rod, said means being engageable with an element of said boom after said initial deflection of said piston rod.
3. The telescopic boom of claim 2, said means slidable on said piston rod comprising vertically extending means having the upper end thereof vertically spaced below the top of the boom when the hydraulic motor is retracted and engaging said top of the boom when the boom is extended and under load.
4. The telescopic boom of claim 2, and means connected to a movable element of said boom and to said slidable means for sliding said slidable means along said piston rod.
5. A multi-section lifting boom for cranes or the like comprising:
at least two sections in telescopic relation, a hydraulic ram having a cylinder and piston rod, means connecting said cylinder to one said section and said piston rod to the other said section, for extension and retraction of one said section relative to the other, said piston rod being subject to deflection when said hydraulic ram is extended and said boom is under load, and means for limiting the deflection of said piston rod to a predetermined amount after initial deflection when said ram is extended and said boom is under load comprising;
means slidable on said piston rod, said means being engageable with an element of said boom after said initial deflection of said piston rod.
at least two sections in telescopic relation, a hydraulic ram having a cylinder and piston rod, means connecting said cylinder to one said section and said piston rod to the other said section, for extension and retraction of one said section relative to the other, said piston rod being subject to deflection when said hydraulic ram is extended and said boom is under load, and means for limiting the deflection of said piston rod to a predetermined amount after initial deflection when said ram is extended and said boom is under load comprising;
means slidable on said piston rod, said means being engageable with an element of said boom after said initial deflection of said piston rod.
6. In a multi-section lifting boom having at least two sections in telescopic relation and a hydraulic ram having a cylinder and piston rod each connected to one said section for extension and retraction of one said section relative to the other, and wherein said piston rod is subject to deflection when said hydraulic ram is extended and said boom is under load, the improvement comprising:
means for limiting the deflection of said piston rod to a predetermined amount after initial deflection thereof when said ram is extended and said boom is under load, said deflection limiting means comprising means movable along said piston rod, and means actuated by said ram cylinder for moving said deflection limiting means along said piston rod.
means for limiting the deflection of said piston rod to a predetermined amount after initial deflection thereof when said ram is extended and said boom is under load, said deflection limiting means comprising means movable along said piston rod, and means actuated by said ram cylinder for moving said deflection limiting means along said piston rod.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA346,322A CA1093506A (en) | 1977-05-12 | 1980-02-18 | Multi-section lifting boom |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/796,381 US4132040A (en) | 1977-05-12 | 1977-05-12 | Multi-section lifting boom |
| US796,381 | 1977-05-12 | ||
| CA303,198A CA1088465A (en) | 1977-05-12 | 1978-05-12 | Multi-section lifting boom |
| CA346,322A CA1093506A (en) | 1977-05-12 | 1980-02-18 | Multi-section lifting boom |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1093506A true CA1093506A (en) | 1981-01-13 |
Family
ID=27165655
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA346,322A Expired CA1093506A (en) | 1977-05-12 | 1980-02-18 | Multi-section lifting boom |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1093506A (en) |
-
1980
- 1980-02-18 CA CA346,322A patent/CA1093506A/en not_active Expired
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